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   * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.  Oracle designates this
   * particular file as subject to the "Classpath" exception as provided
   * by Oracle in the LICENSE file that accompanied this code.
   *
   * This code is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   */
  
  package java.util;
  
  import java.io.IOException;
  import java.io.InvalidObjectException;
  import java.io.Serializable;
  import java.lang.reflect.ParameterizedType;
  import java.lang.reflect.Type;
  import java.util.function.BiConsumer;
  import java.util.function.BiFunction;
  import java.util.function.Consumer;
  import java.util.function.Function;
  
  /**
   * Hash table based implementation of the <tt>Map</tt> interface.  This
   * implementation provides all of the optional map operations, and permits
   * <tt>null</tt> values and the <tt>null</tt> key.  (The <tt>HashMap</tt>
   * class is roughly equivalent to <tt>Hashtable</tt>, except that it is
   * unsynchronized and permits nulls.)  This class makes no guarantees as to
   * the order of the map; in particular, it does not guarantee that the order
   * will remain constant over time.
   *
   * <p>This implementation provides constant-time performance for the basic
   * operations (<tt>get</tt> and <tt>put</tt>), assuming the hash function
   * disperses the elements properly among the buckets.  Iteration over
   * collection views requires time proportional to the "capacity" of the
   * <tt>HashMap</tt> instance (the number of buckets) plus its size (the number
   * of key-value mappings).  Thus, it's very important not to set the initial
   * capacity too high (or the load factor too low) if iteration performance is
   * important.
   *
   * <p>An instance of <tt>HashMap</tt> has two parameters that affect its
   * performance: <i>initial capacity</i> and <i>load factor</i>.  The
   * <i>capacity</i> is the number of buckets in the hash table, and the initial
   * capacity is simply the capacity at the time the hash table is created.  The
   * <i>load factor</i> is a measure of how full the hash table is allowed to
   * get before its capacity is automatically increased.  When the number of
   * entries in the hash table exceeds the product of the load factor and the
   * current capacity, the hash table is <i>rehashed</i> (that is, internal data
   * structures are rebuilt) so that the hash table has approximately twice the
   * number of buckets.
   *
   * <p>As a general rule, the default load factor (.75) offers a good
   * tradeoff between time and space costs.  Higher values decrease the
   * space overhead but increase the lookup cost (reflected in most of
   * the operations of the <tt>HashMap</tt> class, including
   * <tt>get</tt> and <tt>put</tt>).  The expected number of entries in
   * the map and its load factor should be taken into account when
   * setting its initial capacity, so as to minimize the number of
   * rehash operations.  If the initial capacity is greater than the
   * maximum number of entries divided by the load factor, no rehash
   * operations will ever occur.
   *
   * <p>If many mappings are to be stored in a <tt>HashMap</tt>
   * instance, creating it with a sufficiently large capacity will allow
   * the mappings to be stored more efficiently than letting it perform
   * automatic rehashing as needed to grow the table.  Note that using
   * many keys with the same {@code hashCode()} is a sure way to slow
   * down performance of any hash table. To ameliorate impact, when keys
   * are {@link Comparable}, this class may use comparison order among
   * keys to help break ties.
   *
   * <p><strong>Note that this implementation is not synchronized.</strong>
   * If multiple threads access a hash map concurrently, and at least one of
   * the threads modifies the map structurally, it <i>must</i> be
   * synchronized externally.  (A structural modification is any operation
   * that adds or deletes one or more mappings; merely changing the value
   * associated with a key that an instance already contains is not a
   * structural modification.)  This is typically accomplished by
   * synchronizing on some object that naturally encapsulates the map.
   *
   * If no such object exists, the map should be "wrapped" using the
   * {@link Collections#synchronizedMap Collections.synchronizedMap}
   * method.  This is best done at creation time, to prevent accidental
   * unsynchronized access to the map:<pre>
   *   Map m = Collections.synchronizedMap(new HashMap(...));</pre>
   *
   * <p>The iterators returned by all of this class's "collection view methods"
   * are <i>fail-fast</i>: if the map is structurally modified at any time after
   * the iterator is created, in any way except through the iterator's own
   * <tt>remove</tt> method, the iterator will throw a
   * {@link ConcurrentModificationException}.  Thus, in the face of concurrent
   * modification, the iterator fails quickly and cleanly, rather than risking
   * arbitrary, non-deterministic behavior at an undetermined time in the
   * future.
   *
   * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
   * as it is, generally speaking, impossible to make any hard guarantees in the
   * presence of unsynchronized concurrent modification.  Fail-fast iterators
   * throw <tt>ConcurrentModificationException</tt> on a best-effort basis.
   * Therefore, it would be wrong to write a program that depended on this
   * exception for its correctness: <i>the fail-fast behavior of iterators
   * should be used only to detect bugs.</i>
   *
   * <p>This class is a member of the
   * <a href="{@docRoot}/../technotes/guides/collections/index.html">
   * Java Collections Framework</a>.
   *
   * @param <K> the type of keys maintained by this map
   * @param <V> the type of mapped values
   *
   * @author  Doug Lea
   * @author  Josh Bloch
   * @author  Arthur van Hoff
   * @author  Neal Gafter
   * @see     Object#hashCode()
   * @see     Collection
   * @see     Map
   * @see     TreeMap
   * @see     Hashtable
   * @since   1.2
   */
  public class HashMap<K,V> extends AbstractMap<K,V>
      implements Map<K,V>, Cloneable, Serializable {
  
      private static final long serialVersionUID = 362498820763181265L;
  
      /*
       * Implementation notes.
       *
       * This map usually acts as a binned (bucketed) hash table, but
       * when bins get too large, they are transformed into bins of
       * TreeNodes, each structured similarly to those in
       * java.util.TreeMap. Most methods try to use normal bins, but
       * relay to TreeNode methods when applicable (simply by checking
       * instanceof a node).  Bins of TreeNodes may be traversed and
       * used like any others, but additionally support faster lookup
       * when overpopulated. However, since the vast majority of bins in
       * normal use are not overpopulated, checking for existence of
       * tree bins may be delayed in the course of table methods.
       *
       * Tree bins (i.e., bins whose elements are all TreeNodes) are
       * ordered primarily by hashCode, but in the case of ties, if two
       * elements are of the same "class C implements Comparable<C>",
       * type then their compareTo method is used for ordering. (We
       * conservatively check generic types via reflection to validate
       * this -- see method comparableClassFor).  The added complexity
       * of tree bins is worthwhile in providing worst-case O(log n)
       * operations when keys either have distinct hashes or are
       * orderable, Thus, performance degrades gracefully under
       * accidental or malicious usages in which hashCode() methods
       * return values that are poorly distributed, as well as those in
       * which many keys share a hashCode, so long as they are also
       * Comparable. (If neither of these apply, we may waste about a
       * factor of two in time and space compared to taking no
       * precautions. But the only known cases stem from poor user
       * programming practices that are already so slow that this makes
       * little difference.)
       *
       * Because TreeNodes are about twice the size of regular nodes, we
       * use them only when bins contain enough nodes to warrant use
       * (see TREEIFY_THRESHOLD). And when they become too small (due to
       * removal or resizing) they are converted back to plain bins.  In
       * usages with well-distributed user hashCodes, tree bins are
       * rarely used.  Ideally, under random hashCodes, the frequency of
       * nodes in bins follows a Poisson distribution
       * (http://en.wikipedia.org/wiki/Poisson_distribution) with a
       * parameter of about 0.5 on average for the default resizing
       * threshold of 0.75, although with a large variance because of
       * resizing granularity. Ignoring variance, the expected
       * occurrences of list size k are (exp(-0.5) * pow(0.5, k) /
       * factorial(k)). The first values are:
       *
       * 0:    0.60653066
       * 1:    0.30326533
       * 2:    0.07581633
       * 3:    0.01263606
       * 4:    0.00157952
       * 5:    0.00015795
       * 6:    0.00001316
       * 7:    0.00000094
       * 8:    0.00000006
       * more: less than 1 in ten million
       *
       * The root of a tree bin is normally its first node.  However,
       * sometimes (currently only upon Iterator.remove), the root might
       * be elsewhere, but can be recovered following parent links
       * (method TreeNode.root()).
       *
       * All applicable internal methods accept a hash code as an
       * argument (as normally supplied from a public method), allowing
       * them to call each other without recomputing user hashCodes.
       * Most internal methods also accept a "tab" argument, that is
       * normally the current table, but may be a new or old one when
       * resizing or converting.
       *
       * When bin lists are treeified, split, or untreeified, we keep
       * them in the same relative access/traversal order (i.e., field
       * Node.next) to better preserve locality, and to slightly
       * simplify handling of splits and traversals that invoke
       * iterator.remove. When using comparators on insertion, to keep a
       * total ordering (or as close as is required here) across
       * rebalancings, we compare classes and identityHashCodes as
       * tie-breakers.
       *
       * The use and transitions among plain vs tree modes is
       * complicated by the existence of subclass LinkedHashMap. See
       * below for hook methods defined to be invoked upon insertion,
       * removal and access that allow LinkedHashMap internals to
       * otherwise remain independent of these mechanics. (This also
       * requires that a map instance be passed to some utility methods
       * that may create new nodes.)
       *
       * The concurrent-programming-like SSA-based coding style helps
       * avoid aliasing errors amid all of the twisty pointer operations.
       */
  
      /**
       * The default initial capacity - MUST be a power of two.
       */
      static final int DEFAULT_INITIAL_CAPACITY = 1 << 4; // aka 16
  
      /**
       * The maximum capacity, used if a higher value is implicitly specified
       * by either of the constructors with arguments.
       * MUST be a power of two <= 1<<30.
       */
      static final int MAXIMUM_CAPACITY = 1 << 30;
  
      /**
       * The load factor used when none specified in constructor.
       */
      static final float DEFAULT_LOAD_FACTOR = 0.75f;
  
      /**
       * The bin count threshold for using a tree rather than list for a
       * bin.  Bins are converted to trees when adding an element to a
       * bin with at least this many nodes. The value must be greater
       * than 2 and should be at least 8 to mesh with assumptions in
       * tree removal about conversion back to plain bins upon
       * shrinkage.
       */
      static final int TREEIFY_THRESHOLD = 8;
  
      /**
       * The bin count threshold for untreeifying a (split) bin during a
       * resize operation. Should be less than TREEIFY_THRESHOLD, and at
       * most 6 to mesh with shrinkage detection under removal.
       */
      static final int UNTREEIFY_THRESHOLD = 6;
  
      /**
       * The smallest table capacity for which bins may be treeified.
       * (Otherwise the table is resized if too many nodes in a bin.)
       * Should be at least 4 * TREEIFY_THRESHOLD to avoid conflicts
       * between resizing and treeification thresholds.
       */
      static final int MIN_TREEIFY_CAPACITY = 64;
  
      /**
       * Basic hash bin node, used for most entries.  (See below for
       * TreeNode subclass, and in LinkedHashMap for its Entry subclass.)
       */
      static class Node<K,V> implements Entry<K,V> {
          final int hash;
          final K key;
          V value;
          Node<K,V> next;
  
          Node(int hash, K key, V value, Node<K,V> next) {
              this.hash = hash;
              this.key = key;
              this.value = value;
              this.next = next;
          }
  
          public final K getKey()        { return key; }
          public final V getValue()      { return value; }
          public final String toString() { return key + "=" + value; }
  
          public final int hashCode() {
              return Objects.hashCode(key) ^ Objects.hashCode(value);
          }
  
          public final V setValue(V newValue) {
              V oldValue = value;
              value = newValue;
              return oldValue;
          }
  
          public final boolean equals(Object o) {
              if (o == this)
                  return true;
              if (o instanceof Map.Entry) {
                  Entry<?,?> e = (Entry<?,?>)o;
                  if (Objects.equals(key, e.getKey()) &&
                      Objects.equals(value, e.getValue()))
                      return true;
              }
              return false;
          }
      }
  
      /* ---------------- Static utilities -------------- */
  
      /**
       * Computes key.hashCode() and spreads (XORs) higher bits of hash
       * to lower.  Because the table uses power-of-two masking, sets of
       * hashes that vary only in bits above the current mask will
       * always collide. (Among known examples are sets of Float keys
       * holding consecutive whole numbers in small tables.)  So we
       * apply a transform that spreads the impact of higher bits
       * downward. There is a tradeoff between speed, utility, and
       * quality of bit-spreading. Because many common sets of hashes
       * are already reasonably distributed (so don't benefit from
       * spreading), and because we use trees to handle large sets of
       * collisions in bins, we just XOR some shifted bits in the
       * cheapest possible way to reduce systematic lossage, as well as
       * to incorporate impact of the highest bits that would otherwise
       * never be used in index calculations because of table bounds.
       */
      static final int hash(Object key) {
          int h;
          return (key == null) ? 0 : (h = key.hashCode()) ^ (h >>> 16);
      }
  
      /**
       * Returns x's Class if it is of the form "class C implements
       * Comparable<C>", else null.
       */
      static Class<?> comparableClassFor(Object x) {
          if (x instanceof Comparable) {
              Class<?> c; Type[] ts, as; Type t; ParameterizedType p;
              if ((c = x.getClass()) == String.class) // bypass checks
                  return c;
              if ((ts = c.getGenericInterfaces()) != null) {
                  for (int i = 0; i < ts.length; ++i) {
                      if (((t = ts[i]) instanceof ParameterizedType) &&
                          ((p = (ParameterizedType)t).getRawType() ==
                           Comparable.class) &&
                          (as = p.getActualTypeArguments()) != null &&
                          as.length == 1 && as[0] == c) // type arg is c
                          return c;
                  }
              }
          }
          return null;
      }
  
      /**
       * Returns k.compareTo(x) if x matches kc (k's screened comparable
       * class), else 0.
       */
      @SuppressWarnings({"rawtypes","unchecked"}) // for cast to Comparable
      static int compareComparables(Class<?> kc, Object k, Object x) {
          return (x == null || x.getClass() != kc ? 0 :
                  ((Comparable)k).compareTo(x));
      }
  
      /**
       * Returns a power of two size for the given target capacity.
       */
      static final int tableSizeFor(int cap) {
          int n = cap - 1;
          n |= n >>> 1;
          n |= n >>> 2;
          n |= n >>> 4;
          n |= n >>> 8;
          n |= n >>> 16;
          return (n < 0) ? 1 : (n >= MAXIMUM_CAPACITY) ? MAXIMUM_CAPACITY : n + 1;
      }
  
      /* ---------------- Fields -------------- */
  
      /**
       * The table, initialized on first use, and resized as
       * necessary. When allocated, length is always a power of two.
       * (We also tolerate length zero in some operations to allow
       * bootstrapping mechanics that are currently not needed.)
       */
      transient Node<K,V>[] table;
  
      /**
       * Holds cached entrySet(). Note that AbstractMap fields are used
       * for keySet() and values().
       */
      transient Set<Entry<K,V>> entrySet;
  
      /**
       * The number of key-value mappings contained in this map.
       */
      transient int size;
  
      /**
       * The number of times this HashMap has been structurally modified
       * Structural modifications are those that change the number of mappings in
       * the HashMap or otherwise modify its internal structure (e.g.,
       * rehash).  This field is used to make iterators on Collection-views of
       * the HashMap fail-fast.  (See ConcurrentModificationException).
       */
      transient int modCount;
  
      /**
       * The next size value at which to resize (capacity * load factor).
       *
       * @serial
       */
      // (The javadoc description is true upon serialization.
      // Additionally, if the table array has not been allocated, this
      // field holds the initial array capacity, or zero signifying
      // DEFAULT_INITIAL_CAPACITY.)
      int threshold;
  
      /**
       * The load factor for the hash table.
       *
       * @serial
       */
      final float loadFactor;
  
      /* ---------------- Public operations -------------- */
  
      /**
       * Constructs an empty <tt>HashMap</tt> with the specified initial
       * capacity and load factor.
       *
       * @param  initialCapacity the initial capacity
       * @param  loadFactor      the load factor
       * @throws IllegalArgumentException if the initial capacity is negative
       *         or the load factor is nonpositive
       */
      public HashMap(int initialCapacity, float loadFactor) {
          if (initialCapacity < 0)
              throw new IllegalArgumentException("Illegal initial capacity: " +
                                                 initialCapacity);
          if (initialCapacity > MAXIMUM_CAPACITY)
              initialCapacity = MAXIMUM_CAPACITY;
          if (loadFactor <= 0 || Float.isNaN(loadFactor))
              throw new IllegalArgumentException("Illegal load factor: " +
                                                 loadFactor);
          this.loadFactor = loadFactor;
          this.threshold = tableSizeFor(initialCapacity);
      }
  
      /**
       * Constructs an empty <tt>HashMap</tt> with the specified initial
       * capacity and the default load factor (0.75).
       *
       * @param  initialCapacity the initial capacity.
       * @throws IllegalArgumentException if the initial capacity is negative.
       */
      public HashMap(int initialCapacity) {
          this(initialCapacity, DEFAULT_LOAD_FACTOR);
      }
  
      /**
       * Constructs an empty <tt>HashMap</tt> with the default initial capacity
       * (16) and the default load factor (0.75).
       */
      public HashMap() {
          this.loadFactor = DEFAULT_LOAD_FACTOR; // all other fields defaulted
      }
  
      /**
       * Constructs a new <tt>HashMap</tt> with the same mappings as the
       * specified <tt>Map</tt>.  The <tt>HashMap</tt> is created with
       * default load factor (0.75) and an initial capacity sufficient to
       * hold the mappings in the specified <tt>Map</tt>.
       *
       * @param   m the map whose mappings are to be placed in this map
       * @throws  NullPointerException if the specified map is null
       */
      public HashMap(Map<? extends K, ? extends V> m) {
          this.loadFactor = DEFAULT_LOAD_FACTOR;
          putMapEntries(m, false);
      }
  
      /**
       * Implements Map.putAll and Map constructor
       *
       * @param m the map
       * @param evict false when initially constructing this map, else
       * true (relayed to method afterNodeInsertion).
       */
      final void putMapEntries(Map<? extends K, ? extends V> m, boolean evict) {
          int s = m.size();
          if (s > 0) {
              if (table == null) { // pre-size
                  float ft = ((float)s / loadFactor) + 1.0F;
                  int t = ((ft < (float)MAXIMUM_CAPACITY) ?
                           (int)ft : MAXIMUM_CAPACITY);
                  if (t > threshold)
                      threshold = tableSizeFor(t);
              }
              else if (s > threshold)
                  resize();
              for (Entry<? extends K, ? extends V> e : m.entrySet()) {
                  K key = e.getKey();
                  V value = e.getValue();
                  putVal(hash(key), key, value, false, evict);
              }
          }
      }
  
      /**
       * Returns the number of key-value mappings in this map.
       *
       * @return the number of key-value mappings in this map
       */
      public int size() {
          return size;
      }
  
      /**
       * Returns <tt>true</tt> if this map contains no key-value mappings.
       *
       * @return <tt>true</tt> if this map contains no key-value mappings
       */
      public boolean isEmpty() {
          return size == 0;
      }
  
      /**
       * Returns the value to which the specified key is mapped,
       * or {@code null} if this map contains no mapping for the key.
       *
       * <p>More formally, if this map contains a mapping from a key
       * {@code k} to a value {@code v} such that {@code (key==null ? k==null :
       * key.equals(k))}, then this method returns {@code v}; otherwise
       * it returns {@code null}.  (There can be at most one such mapping.)
       *
       * <p>A return value of {@code null} does not <i>necessarily</i>
       * indicate that the map contains no mapping for the key; it's also
       * possible that the map explicitly maps the key to {@code null}.
       * The {@link #containsKey containsKey} operation may be used to
       * distinguish these two cases.
       *
       * @see #put(Object, Object)
       */
      public V get(Object key) {
          Node<K,V> e;
          return (e = getNode(hash(key), key)) == null ? null : e.value;
      }
  
      /**
       * Implements Map.get and related methods
       *
       * @param hash hash for key
       * @param key the key
       * @return the node, or null if none
       */
      final Node<K,V> getNode(int hash, Object key) {
          Node<K,V>[] tab; Node<K,V> first, e; int n; K k;
          if ((tab = table) != null && (n = tab.length) > 0 &&
              (first = tab[(n - 1) & hash]) != null) {
              if (first.hash == hash && // always check first node
                  ((k = first.key) == key || (key != null && key.equals(k))))
                  return first;
              if ((e = first.next) != null) {
                  if (first instanceof TreeNode)
                      return ((TreeNode<K,V>)first).getTreeNode(hash, key);
                  do {
                      if (e.hash == hash &&
                          ((k = e.key) == key || (key != null && key.equals(k))))
                          return e;
                  } while ((e = e.next) != null);
              }
          }
          return null;
      }
  
      /**
       * Returns <tt>true</tt> if this map contains a mapping for the
       * specified key.
       *
       * @param   key   The key whose presence in this map is to be tested
       * @return <tt>true</tt> if this map contains a mapping for the specified
       * key.
       */
      public boolean containsKey(Object key) {
          return getNode(hash(key), key) != null;
      }
  
      /**
       * Associates the specified value with the specified key in this map.
       * If the map previously contained a mapping for the key, the old
       * value is replaced.
       *
       * @param key key with which the specified value is to be associated
       * @param value value to be associated with the specified key
       * @return the previous value associated with <tt>key</tt>, or
       *         <tt>null</tt> if there was no mapping for <tt>key</tt>.
       *         (A <tt>null</tt> return can also indicate that the map
       *         previously associated <tt>null</tt> with <tt>key</tt>.)
       */
      public V put(K key, V value) {
          return putVal(hash(key), key, value, false, true);
      }
  
      /**
       * Implements Map.put and related methods
       *
       * @param hash hash for key
       * @param key the key
       * @param value the value to put
       * @param onlyIfAbsent if true, don't change existing value
       * @param evict if false, the table is in creation mode.
       * @return previous value, or null if none
       */
      final V putVal(int hash, K key, V value, boolean onlyIfAbsent,
                     boolean evict) {
          Node<K,V>[] tab; Node<K,V> p; int n, i;
          if ((tab = table) == null || (n = tab.length) == 0)
              n = (tab = resize()).length;
          if ((p = tab[i = (n - 1) & hash]) == null)
              tab[i] = newNode(hash, key, value, null);
          else {
              Node<K,V> e; K k;
              if (p.hash == hash &&
                  ((k = p.key) == key || (key != null && key.equals(k))))
                  e = p;
              else if (p instanceof TreeNode)
                  e = ((TreeNode<K,V>)p).putTreeVal(this, tab, hash, key, value);
              else {
                  for (int binCount = 0; ; ++binCount) {
                      if ((e = p.next) == null) {
                          p.next = newNode(hash, key, value, null);
                          if (binCount >= TREEIFY_THRESHOLD - 1) // -1 for 1st
                              treeifyBin(tab, hash);
                          break;
                      }
                      if (e.hash == hash &&
                          ((k = e.key) == key || (key != null && key.equals(k))))
                          break;
                      p = e;
                  }
              }
              if (e != null) { // existing mapping for key
                  V oldValue = e.value;
                  if (!onlyIfAbsent || oldValue == null)
                      e.value = value;
                  afterNodeAccess(e);
                  return oldValue;
              }
          }
          ++modCount;
          if (++size > threshold)
              resize();
          afterNodeInsertion(evict);
          return null;
      }
  
      /**
       * Initializes or doubles table size.  If null, allocates in
       * accord with initial capacity target held in field threshold.
       * Otherwise, because we are using power-of-two expansion, the
       * elements from each bin must either stay at same index, or move
       * with a power of two offset in the new table.
       *
       * @return the table
       */
      final Node<K,V>[] resize() {
          Node<K,V>[] oldTab = table;
          int oldCap = (oldTab == null) ? 0 : oldTab.length;
          int oldThr = threshold;
          int newCap, newThr = 0;
          if (oldCap > 0) {
              if (oldCap >= MAXIMUM_CAPACITY) {
                  threshold = Integer.MAX_VALUE;
                  return oldTab;
              }
              else if ((newCap = oldCap << 1) < MAXIMUM_CAPACITY &&
                       oldCap >= DEFAULT_INITIAL_CAPACITY)
                  newThr = oldThr << 1; // double threshold
          }
          else if (oldThr > 0) // initial capacity was placed in threshold
              newCap = oldThr;
          else {               // zero initial threshold signifies using defaults
              newCap = DEFAULT_INITIAL_CAPACITY;
              newThr = (int)(DEFAULT_LOAD_FACTOR * DEFAULT_INITIAL_CAPACITY);
          }
          if (newThr == 0) {
              float ft = (float)newCap * loadFactor;
              newThr = (newCap < MAXIMUM_CAPACITY && ft < (float)MAXIMUM_CAPACITY ?
                        (int)ft : Integer.MAX_VALUE);
          }
          threshold = newThr;
          @SuppressWarnings({"rawtypes","unchecked"})
              Node<K,V>[] newTab = (Node<K,V>[])new Node[newCap];
          table = newTab;
          if (oldTab != null) {
              for (int j = 0; j < oldCap; ++j) {
                  Node<K,V> e;
                  if ((e = oldTab[j]) != null) {
                      oldTab[j] = null;
                      if (e.next == null)
                          newTab[e.hash & (newCap - 1)] = e;
                      else if (e instanceof TreeNode)
                          ((TreeNode<K,V>)e).split(this, newTab, j, oldCap);
                      else { // preserve order
                          Node<K,V> loHead = null, loTail = null;
                          Node<K,V> hiHead = null, hiTail = null;
                          Node<K,V> next;
                          do {
                              next = e.next;
                              if ((e.hash & oldCap) == 0) {
                                  if (loTail == null)
                                      loHead = e;
                                  else
                                      loTail.next = e;
                                  loTail = e;
                              }
                              else {
                                  if (hiTail == null)
                                      hiHead = e;
                                  else
                                      hiTail.next = e;
                                  hiTail = e;
                              }
                          } while ((e = next) != null);
                          if (loTail != null) {
                              loTail.next = null;
                              newTab[j] = loHead;
                          }
                          if (hiTail != null) {
                              hiTail.next = null;
                              newTab[j + oldCap] = hiHead;
                          }
                      }
                  }
              }
          }
          return newTab;
      }
  
      /**
       * Replaces all linked nodes in bin at index for given hash unless
       * table is too small, in which case resizes instead.
       */
      final void treeifyBin(Node<K,V>[] tab, int hash) {
          int n, index; Node<K,V> e;
          if (tab == null || (n = tab.length) < MIN_TREEIFY_CAPACITY)
              resize();
          else if ((e = tab[index = (n - 1) & hash]) != null) {
              TreeNode<K,V> hd = null, tl = null;
              do {
                  TreeNode<K,V> p = replacementTreeNode(e, null);
                  if (tl == null)
                      hd = p;
                  else {
                      p.prev = tl;
                      tl.next = p;
                  }
                  tl = p;
              } while ((e = e.next) != null);
              if ((tab[index] = hd) != null)
                  hd.treeify(tab);
          }
      }
  
      /**
       * Copies all of the mappings from the specified map to this map.
       * These mappings will replace any mappings that this map had for
       * any of the keys currently in the specified map.
       *
       * @param m mappings to be stored in this map
       * @throws NullPointerException if the specified map is null
       */
      public void putAll(Map<? extends K, ? extends V> m) {
          putMapEntries(m, true);
      }
  
      /**
       * Removes the mapping for the specified key from this map if present.
       *
       * @param  key key whose mapping is to be removed from the map
       * @return the previous value associated with <tt>key</tt>, or
       *         <tt>null</tt> if there was no mapping for <tt>key</tt>.
       *         (A <tt>null</tt> return can also indicate that the map
       *         previously associated <tt>null</tt> with <tt>key</tt>.)
       */
      public V remove(Object key) {
          Node<K,V> e;
          return (e = removeNode(hash(key), key, null, false, true)) == null ?
              null : e.value;
      }
  
      /**
       * Implements Map.remove and related methods
       *
       * @param hash hash for key
       * @param key the key
       * @param value the value to match if matchValue, else ignored
       * @param matchValue if true only remove if value is equal
       * @param movable if false do not move other nodes while removing
       * @return the node, or null if none
       */
      final Node<K,V> removeNode(int hash, Object key, Object value,
                                 boolean matchValue, boolean movable) {
          Node<K,V>[] tab; Node<K,V> p; int n, index;
          if ((tab = table) != null && (n = tab.length) > 0 &&
              (p = tab[index = (n - 1) & hash]) != null) {
              Node<K,V> node = null, e; K k; V v;
              if (p.hash == hash &&
                  ((k = p.key) == key || (key != null && key.equals(k))))
                  node = p;
              else if ((e = p.next) != null) {
                  if (p instanceof TreeNode)
                      node = ((TreeNode<K,V>)p).getTreeNode(hash, key);
                  else {
                      do {
                          if (e.hash == hash &&
                              ((k = e.key) == key ||
                               (key != null && key.equals(k)))) {
                              node = e;
                              break;
                          }
                          p = e;
                      } while ((e = e.next) != null);
                  }
              }
              if (node != null && (!matchValue || (v = node.value) == value ||
                                   (value != null && value.equals(v)))) {
                  if (node instanceof TreeNode)
                      ((TreeNode<K,V>)node).removeTreeNode(this, tab, movable);
                  else if (node == p)
                      tab[index] = node.next;
                  else
                      p.next = node.next;
                  ++modCount;
                  --size;
                  afterNodeRemoval(node);
                  return node;
              }
          }
          return null;
      }
  
      /**
       * Removes all of the mappings from this map.
       * The map will be empty after this call returns.
       */
      public void clear() {
          Node<K,V>[] tab;
          modCount++;
          if ((tab = table) != null && size > 0) {
              size = 0;
              for (int i = 0; i < tab.length; ++i)
                  tab[i] = null;
          }
      }
  
      /**
       * Returns <tt>true</tt> if this map maps one or more keys to the
       * specified value.
       *
       * @param value value whose presence in this map is to be tested
       * @return <tt>true</tt> if this map maps one or more keys to the
       *         specified value
       */
      public boolean containsValue(Object value) {
          Node<K,V>[] tab; V v;
          if ((tab = table) != null && size > 0) {
              for (int i = 0; i < tab.length; ++i) {
                  for (Node<K,V> e = tab[i]; e != null; e = e.next) {
                      if ((v = e.value) == value ||
                          (value != null && value.equals(v)))
                          return true;
                  }
              }
          }
          return false;
      }
  
      /**
       * Returns a {@link Set} view of the keys contained in this map.
       * The set is backed by the map, so changes to the map are
       * reflected in the set, and vice-versa.  If the map is modified
       * while an iteration over the set is in progress (except through
       * the iterator's own <tt>remove</tt> operation), the results of
       * the iteration are undefined.  The set supports element removal,
       * which removes the corresponding mapping from the map, via the
       * <tt>Iterator.remove</tt>, <tt>Set.remove</tt>,
       * <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
       * operations.  It does not support the <tt>add</tt> or <tt>addAll</tt>
       * operations.
       *
       * @return a set view of the keys contained in this map
       */
      public Set<K> keySet() {
          Set<K> ks = keySet;
          if (ks == null) {
              ks = new KeySet();
              keySet = ks;
          }
          return ks;
      }
  
      final class KeySet extends AbstractSet<K> {
          public final int size()                 { return size; }
          public final void clear()               { HashMap.this.clear(); }
          public final Iterator<K> iterator()     { return new KeyIterator(); }
          public final boolean contains(Object o) { return containsKey(o); }
          public final boolean remove(Object key) {
              return removeNode(hash(key), key, null, false, true) != null;
          }
          public final Spliterator<K> spliterator() {
              return new KeySpliterator<>(HashMap.this, 0, -1, 0, 0);
          }
          public final void forEach(Consumer<? super K> action) {
              Node<K,V>[] tab;
              if (action == null)
                  throw new NullPointerException();
              if (size > 0 && (tab = table) != null) {
                  int mc = modCount;
                  // Android-changed: Detect changes to modCount early.
                  for (int i = 0; (i < tab.length && modCount == mc); ++i) {
                      for (Node<K,V> e = tab[i]; e != null; e = e.next)
                          action.accept(e.key);
                  }
                  if (modCount != mc)
                      throw new ConcurrentModificationException();
              }
          }
      }
  
      /**
       * Returns a {@link Collection} view of the values contained in this map.
       * The collection is backed by the map, so changes to the map are
       * reflected in the collection, and vice-versa.  If the map is
       * modified while an iteration over the collection is in progress
       * (except through the iterator's own <tt>remove</tt> operation),
       * the results of the iteration are undefined.  The collection
       * supports element removal, which removes the corresponding
       * mapping from the map, via the <tt>Iterator.remove</tt>,
       * <tt>Collection.remove</tt>, <tt>removeAll</tt>,
       * <tt>retainAll</tt> and <tt>clear</tt> operations.  It does not
       * support the <tt>add</tt> or <tt>addAll</tt> operations.
       *
       * @return a view of the values contained in this map
       */
      public Collection<V> values() {
          Collection<V> vs = values;
          if (vs == null) {
              vs = new Values();
              values = vs;
          }
          return vs;
      }
  
      final class Values extends AbstractCollection<V> {
          public final int size()                 { return size; }
          public final void clear()               { HashMap.this.clear(); }
          public final Iterator<V> iterator()     { return new ValueIterator(); }
          public final boolean contains(Object o) { return containsValue(o); }
          public final Spliterator<V> spliterator() {
              return new ValueSpliterator<>(HashMap.this, 0, -1, 0, 0);
          }
          public final void forEach(Consumer<? super V> action) {
              Node<K,V>[] tab;
              if (action == null)
                  throw new NullPointerException();
              if (size > 0 && (tab = table) != null) {
                  int mc = modCount;
                  // Android-changed: Detect changes to modCount early.
                  for (int i = 0; (i < tab.length && modCount == mc); ++i) {
                      for (Node<K,V> e = tab[i]; e != null; e = e.next)
                          action.accept(e.value);
                  }
                  if (modCount != mc)
                      throw new ConcurrentModificationException();
              }
          }
      }
  
      /**
       * Returns a {@link Set} view of the mappings contained in this map.
       * The set is backed by the map, so changes to the map are
       * reflected in the set, and vice-versa.  If the map is modified
       * while an iteration over the set is in progress (except through
       * the iterator's own <tt>remove</tt> operation, or through the
       * <tt>setValue</tt> operation on a map entry returned by the
       * iterator) the results of the iteration are undefined.  The set
       * supports element removal, which removes the corresponding
       * mapping from the map, via the <tt>Iterator.remove</tt>,
       * <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt> and
       * <tt>clear</tt> operations.  It does not support the
       * <tt>add</tt> or <tt>addAll</tt> operations.
       *
       * @return a set view of the mappings contained in this map
       */
      public Set<Entry<K,V>> entrySet() {
          Set<Entry<K,V>> es;
          return (es = entrySet) == null ? (entrySet = new EntrySet()) : es;
      }
  
      final class EntrySet extends AbstractSet<Entry<K,V>> {
          public final int size()                 { return size; }
          public final void clear()               { HashMap.this.clear(); }
          public final Iterator<Entry<K,V>> iterator() {
              return new EntryIterator();
          }
          public final boolean contains(Object o) {
              if (!(o instanceof Map.Entry))
                  return false;
              Entry<?,?> e = (Entry<?,?>) o;
              Object key = e.getKey();
              Node<K,V> candidate = getNode(hash(key), key);
              return candidate != null && candidate.equals(e);
          }
          public final boolean remove(Object o) {
              if (o instanceof Map.Entry) {
                  Entry<?,?> e = (Entry<?,?>) o;
                  Object key = e.getKey();
                  Object value = e.getValue();
                  return removeNode(hash(key), key, value, true, true) != null;
              }
              return false;
          }
          public final Spliterator<Entry<K,V>> spliterator() {
              return new EntrySpliterator<>(HashMap.this, 0, -1, 0, 0);
          }
          public final void forEach(Consumer<? super Entry<K,V>> action) {
              Node<K,V>[] tab;
              if (action == null)
                  throw new NullPointerException();
              if (size > 0 && (tab = table) != null) {
                  int mc = modCount;
                  // Android-changed: Detect changes to modCount early.
                  for (int i = 0; (i < tab.length && modCount == mc); ++i) {
                      for (Node<K,V> e = tab[i]; e != null; e = e.next)
                          action.accept(e);
                  }
                  if (modCount != mc)
                      throw new ConcurrentModificationException();
              }
          }
      }
  
      // Overrides of JDK8 Map extension methods
  
      @Override
      public V getOrDefault(Object key, V defaultValue) {
          Node<K,V> e;
          return (e = getNode(hash(key), key)) == null ? defaultValue : e.value;
      }
  
      @Override
      public V putIfAbsent(K key, V value) {
          return putVal(hash(key), key, value, true, true);
      }
  
      @Override
      public boolean remove(Object key, Object value) {
          return removeNode(hash(key), key, value, true, true) != null;
      }
  
      @Override
      public boolean replace(K key, V oldValue, V newValue) {
          Node<K,V> e; V v;
          if ((e = getNode(hash(key), key)) != null &&
              ((v = e.value) == oldValue || (v != null && v.equals(oldValue)))) {
              e.value = newValue;
              afterNodeAccess(e);
              return true;
          }
          return false;
      }
  
      @Override
      public V replace(K key, V value) {
          Node<K,V> e;
          if ((e = getNode(hash(key), key)) != null) {
              V oldValue = e.value;
              e.value = value;
              afterNodeAccess(e);
              return oldValue;
          }
          return null;
      }
  
      @Override
      public V computeIfAbsent(K key,
                               Function<? super K, ? extends V> mappingFunction) {
          if (mappingFunction == null)
              throw new NullPointerException();
          int hash = hash(key);
          Node<K,V>[] tab; Node<K,V> first; int n, i;
          int binCount = 0;
          TreeNode<K,V> t = null;
          Node<K,V> old = null;
          if (size > threshold || (tab = table) == null ||
              (n = tab.length) == 0)
              n = (tab = resize()).length;
          if ((first = tab[i = (n - 1) & hash]) != null) {
              if (first instanceof TreeNode)
                  old = (t = (TreeNode<K,V>)first).getTreeNode(hash, key);
              else {
                  Node<K,V> e = first; K k;
                  do {
                      if (e.hash == hash &&
                          ((k = e.key) == key || (key != null && key.equals(k)))) {
                          old = e;
                          break;
                      }
                      ++binCount;
                  } while ((e = e.next) != null);
              }
              V oldValue;
              if (old != null && (oldValue = old.value) != null) {
                  afterNodeAccess(old);
                  return oldValue;
              }
          }
          V v = mappingFunction.apply(key);
          if (v == null) {
              return null;
          } else if (old != null) {
              old.value = v;
              afterNodeAccess(old);
              return v;
          }
          else if (t != null)
              t.putTreeVal(this, tab, hash, key, v);
          else {
              tab[i] = newNode(hash, key, v, first);
              if (binCount >= TREEIFY_THRESHOLD - 1)
                  treeifyBin(tab, hash);
          }
          ++modCount;
          ++size;
          afterNodeInsertion(true);
          return v;
      }
  
      public V computeIfPresent(K key,
                                BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
          if (remappingFunction == null)
              throw new NullPointerException();
          Node<K,V> e; V oldValue;
          int hash = hash(key);
          if ((e = getNode(hash, key)) != null &&
              (oldValue = e.value) != null) {
              V v = remappingFunction.apply(key, oldValue);
              if (v != null) {
                  e.value = v;
                  afterNodeAccess(e);
                  return v;
              }
              else
                  removeNode(hash, key, null, false, true);
          }
          return null;
      }
  
      @Override
      public V compute(K key,
                       BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
          if (remappingFunction == null)
              throw new NullPointerException();
          int hash = hash(key);
          Node<K,V>[] tab; Node<K,V> first; int n, i;
          int binCount = 0;
          TreeNode<K,V> t = null;
          Node<K,V> old = null;
          if (size > threshold || (tab = table) == null ||
              (n = tab.length) == 0)
              n = (tab = resize()).length;
          if ((first = tab[i = (n - 1) & hash]) != null) {
              if (first instanceof TreeNode)
                  old = (t = (TreeNode<K,V>)first).getTreeNode(hash, key);
              else {
                  Node<K,V> e = first; K k;
                  do {
                      if (e.hash == hash &&
                          ((k = e.key) == key || (key != null && key.equals(k)))) {
                          old = e;
                          break;
                      }
                      ++binCount;
                  } while ((e = e.next) != null);
              }
          }
          V oldValue = (old == null) ? null : old.value;
          V v = remappingFunction.apply(key, oldValue);
          if (old != null) {
              if (v != null) {
                  old.value = v;
                  afterNodeAccess(old);
              }
              else
                  removeNode(hash, key, null, false, true);
          }
          else if (v != null) {
              if (t != null)
                  t.putTreeVal(this, tab, hash, key, v);
              else {
                  tab[i] = newNode(hash, key, v, first);
                  if (binCount >= TREEIFY_THRESHOLD - 1)
                      treeifyBin(tab, hash);
              }
              ++modCount;
              ++size;
              afterNodeInsertion(true);
          }
          return v;
      }
  
      @Override
      public V merge(K key, V value,
                     BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
          if (value == null)
              throw new NullPointerException();
          if (remappingFunction == null)
              throw new NullPointerException();
          int hash = hash(key);
          Node<K,V>[] tab; Node<K,V> first; int n, i;
          int binCount = 0;
          TreeNode<K,V> t = null;
          Node<K,V> old = null;
          if (size > threshold || (tab = table) == null ||
              (n = tab.length) == 0)
              n = (tab = resize()).length;
          if ((first = tab[i = (n - 1) & hash]) != null) {
              if (first instanceof TreeNode)
                  old = (t = (TreeNode<K,V>)first).getTreeNode(hash, key);
              else {
                  Node<K,V> e = first; K k;
                  do {
                      if (e.hash == hash &&
                          ((k = e.key) == key || (key != null && key.equals(k)))) {
                          old = e;
                          break;
                      }
                      ++binCount;
                  } while ((e = e.next) != null);
              }
          }
          if (old != null) {
              V v;
              if (old.value != null)
                  v = remappingFunction.apply(old.value, value);
              else
                  v = value;
              if (v != null) {
                  old.value = v;
                  afterNodeAccess(old);
              }
              else
                  removeNode(hash, key, null, false, true);
              return v;
          }
          if (value != null) {
              if (t != null)
                  t.putTreeVal(this, tab, hash, key, value);
              else {
                  tab[i] = newNode(hash, key, value, first);
                  if (binCount >= TREEIFY_THRESHOLD - 1)
                      treeifyBin(tab, hash);
              }
              ++modCount;
              ++size;
              afterNodeInsertion(true);
          }
          return value;
      }
  
      @Override
      public void forEach(BiConsumer<? super K, ? super V> action) {
          Node<K,V>[] tab;
          if (action == null)
              throw new NullPointerException();
          if (size > 0 && (tab = table) != null) {
              int mc = modCount;
              // Android-changed: Detect changes to modCount early.
              for (int i = 0; (i < tab.length && mc == modCount); ++i) {
                  for (Node<K,V> e = tab[i]; e != null; e = e.next)
                      action.accept(e.key, e.value);
              }
              if (modCount != mc)
                  throw new ConcurrentModificationException();
          }
      }
  
      @Override
      public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
          Node<K,V>[] tab;
          if (function == null)
              throw new NullPointerException();
          if (size > 0 && (tab = table) != null) {
              int mc = modCount;
              for (int i = 0; i < tab.length; ++i) {
                  for (Node<K,V> e = tab[i]; e != null; e = e.next) {
                      e.value = function.apply(e.key, e.value);
                  }
              }
              if (modCount != mc)
                  throw new ConcurrentModificationException();
          }
      }
  
      /* ------------------------------------------------------------ */
      // Cloning and serialization
  
      /**
       * Returns a shallow copy of this <tt>HashMap</tt> instance: the keys and
       * values themselves are not cloned.
       *
       * @return a shallow copy of this map
       */
      @SuppressWarnings("unchecked")
      @Override
      public Object clone() {
          HashMap<K,V> result;
          try {
              result = (HashMap<K,V>)super.clone();
          } catch (CloneNotSupportedException e) {
              // this shouldn't happen, since we are Cloneable
              throw new InternalError(e);
          }
          result.reinitialize();
          result.putMapEntries(this, false);
          return result;
      }
  
      // These methods are also used when serializing HashSets
      final float loadFactor() { return loadFactor; }
      final int capacity() {
          return (table != null) ? table.length :
              (threshold > 0) ? threshold :
              DEFAULT_INITIAL_CAPACITY;
      }
  
      /**
       * Save the state of the <tt>HashMap</tt> instance to a stream (i.e.,
       * serialize it).
       *
       * @serialData The <i>capacity</i> of the HashMap (the length of the
       *             bucket array) is emitted (int), followed by the
       *             <i>size</i> (an int, the number of key-value
       *             mappings), followed by the key (Object) and value (Object)
       *             for each key-value mapping.  The key-value mappings are
       *             emitted in no particular order.
       */
      private void writeObject(java.io.ObjectOutputStream s)
          throws IOException {
          int buckets = capacity();
          // Write out the threshold, loadfactor, and any hidden stuff
          s.defaultWriteObject();
          s.writeInt(buckets);
          s.writeInt(size);
          internalWriteEntries(s);
      }
  
      /**
       * Reconstitute the {@code HashMap} instance from a stream (i.e.,
       * deserialize it).
       */
      private void readObject(java.io.ObjectInputStream s)
          throws IOException, ClassNotFoundException {
          // Read in the threshold (ignored), loadfactor, and any hidden stuff
          s.defaultReadObject();
          reinitialize();
          if (loadFactor <= 0 || Float.isNaN(loadFactor))
              throw new InvalidObjectException("Illegal load factor: " +
                                               loadFactor);
          s.readInt();                // Read and ignore number of buckets
          int mappings = s.readInt(); // Read number of mappings (size)
          if (mappings < 0)
              throw new InvalidObjectException("Illegal mappings count: " +
                                               mappings);
          else if (mappings > 0) { // (if zero, use defaults)
              // Size the table using given load factor only if within
              // range of 0.25...4.0
              float lf = Math.min(Math.max(0.25f, loadFactor), 4.0f);
              float fc = (float)mappings / lf + 1.0f;
              int cap = ((fc < DEFAULT_INITIAL_CAPACITY) ?
                         DEFAULT_INITIAL_CAPACITY :
                         (fc >= MAXIMUM_CAPACITY) ?
                         MAXIMUM_CAPACITY :
                         tableSizeFor((int)fc));
              float ft = (float)cap * lf;
              threshold = ((cap < MAXIMUM_CAPACITY && ft < MAXIMUM_CAPACITY) ?
                           (int)ft : Integer.MAX_VALUE);
              @SuppressWarnings({"rawtypes","unchecked"})
                  Node<K,V>[] tab = (Node<K,V>[])new Node[cap];
              table = tab;
  
              // Read the keys and values, and put the mappings in the HashMap
              for (int i = 0; i < mappings; i++) {
                  @SuppressWarnings("unchecked")
                      K key = (K) s.readObject();
                  @SuppressWarnings("unchecked")
                      V value = (V) s.readObject();
                  putVal(hash(key), key, value, false, false);
              }
          }
      }
  
      /* ------------------------------------------------------------ */
      // iterators
  
      abstract class HashIterator {
          Node<K,V> next;        // next entry to return
          Node<K,V> current;     // current entry
          int expectedModCount;  // for fast-fail
          int index;             // current slot
  
          HashIterator() {
              expectedModCount = modCount;
              Node<K,V>[] t = table;
              current = next = null;
              index = 0;
              if (t != null && size > 0) { // advance to first entry
                  do {} while (index < t.length && (next = t[index++]) == null);
              }
          }
  
          public final boolean hasNext() {
              return next != null;
          }
  
          final Node<K,V> nextNode() {
              Node<K,V>[] t;
              Node<K,V> e = next;
              if (modCount != expectedModCount)
                  throw new ConcurrentModificationException();
              if (e == null)
                  throw new NoSuchElementException();
              if ((next = (current = e).next) == null && (t = table) != null) {
                  do {} while (index < t.length && (next = t[index++]) == null);
              }
              return e;
          }
  
          public final void remove() {
              Node<K,V> p = current;
              if (p == null)
                  throw new IllegalStateException();
              if (modCount != expectedModCount)
                  throw new ConcurrentModificationException();
              current = null;
              K key = p.key;
              removeNode(hash(key), key, null, false, false);
              expectedModCount = modCount;
          }
      }
  
      final class KeyIterator extends HashIterator
          implements Iterator<K> {
          public final K next() { return nextNode().key; }
      }
  
      final class ValueIterator extends HashIterator
          implements Iterator<V> {
          public final V next() { return nextNode().value; }
      }
  
      final class EntryIterator extends HashIterator
          implements Iterator<Entry<K,V>> {
          public final Entry<K,V> next() { return nextNode(); }
      }
  
      /* ------------------------------------------------------------ */
      // spliterators
  
      static class HashMapSpliterator<K,V> {
          final HashMap<K,V> map;
          Node<K,V> current;          // current node
          int index;                  // current index, modified on advance/split
          int fence;                  // one past last index
          int est;                    // size estimate
          int expectedModCount;       // for comodification checks
  
          HashMapSpliterator(HashMap<K,V> m, int origin,
                             int fence, int est,
                             int expectedModCount) {
              this.map = m;
              this.index = origin;
              this.fence = fence;
              this.est = est;
              this.expectedModCount = expectedModCount;
          }
  
          final int getFence() { // initialize fence and size on first use
              int hi;
              if ((hi = fence) < 0) {
                  HashMap<K,V> m = map;
                  est = m.size;
                  expectedModCount = m.modCount;
                  Node<K,V>[] tab = m.table;
                  hi = fence = (tab == null) ? 0 : tab.length;
              }
              return hi;
          }
  
          public final long estimateSize() {
              getFence(); // force init
              return (long) est;
          }
      }
  
      static final class KeySpliterator<K,V>
          extends HashMapSpliterator<K,V>
          implements Spliterator<K> {
          KeySpliterator(HashMap<K,V> m, int origin, int fence, int est,
                         int expectedModCount) {
              super(m, origin, fence, est, expectedModCount);
          }
  
          public KeySpliterator<K,V> trySplit() {
              int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
              return (lo >= mid || current != null) ? null :
                  new KeySpliterator<>(map, lo, index = mid, est >>>= 1,
                                          expectedModCount);
          }
  
          public void forEachRemaining(Consumer<? super K> action) {
              int i, hi, mc;
              if (action == null)
                  throw new NullPointerException();
              HashMap<K,V> m = map;
              Node<K,V>[] tab = m.table;
              if ((hi = fence) < 0) {
                  mc = expectedModCount = m.modCount;
                  hi = fence = (tab == null) ? 0 : tab.length;
              }
              else
                  mc = expectedModCount;
              if (tab != null && tab.length >= hi &&
                  (i = index) >= 0 && (i < (index = hi) || current != null)) {
                  Node<K,V> p = current;
                  current = null;
                  do {
                      if (p == null)
                          p = tab[i++];
                      else {
                          action.accept(p.key);
                          p = p.next;
                      }
                  } while (p != null || i < hi);
                  if (m.modCount != mc)
                      throw new ConcurrentModificationException();
              }
          }
  
          public boolean tryAdvance(Consumer<? super K> action) {
              int hi;
              if (action == null)
                  throw new NullPointerException();
              Node<K,V>[] tab = map.table;
              if (tab != null && tab.length >= (hi = getFence()) && index >= 0) {
                  while (current != null || index < hi) {
                      if (current == null)
                          current = tab[index++];
                      else {
                          K k = current.key;
                          current = current.next;
                          action.accept(k);
                          if (map.modCount != expectedModCount)
                              throw new ConcurrentModificationException();
                          return true;
                      }
                  }
              }
              return false;
          }
  
          public int characteristics() {
              return (fence < 0 || est == map.size ? Spliterator.SIZED : 0) |
                  Spliterator.DISTINCT;
          }
      }
  
      static final class ValueSpliterator<K,V>
          extends HashMapSpliterator<K,V>
          implements Spliterator<V> {
          ValueSpliterator(HashMap<K,V> m, int origin, int fence, int est,
                           int expectedModCount) {
              super(m, origin, fence, est, expectedModCount);
          }
  
          public ValueSpliterator<K,V> trySplit() {
              int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
              return (lo >= mid || current != null) ? null :
                  new ValueSpliterator<>(map, lo, index = mid, est >>>= 1,
                                            expectedModCount);
          }
  
          public void forEachRemaining(Consumer<? super V> action) {
              int i, hi, mc;
              if (action == null)
                  throw new NullPointerException();
              HashMap<K,V> m = map;
              Node<K,V>[] tab = m.table;
              if ((hi = fence) < 0) {
                  mc = expectedModCount = m.modCount;
                  hi = fence = (tab == null) ? 0 : tab.length;
              }
              else
                  mc = expectedModCount;
              if (tab != null && tab.length >= hi &&
                  (i = index) >= 0 && (i < (index = hi) || current != null)) {
                  Node<K,V> p = current;
                  current = null;
                  do {
                      if (p == null)
                          p = tab[i++];
                      else {
                          action.accept(p.value);
                          p = p.next;
                      }
                  } while (p != null || i < hi);
                  if (m.modCount != mc)
                      throw new ConcurrentModificationException();
              }
          }
  
          public boolean tryAdvance(Consumer<? super V> action) {
              int hi;
              if (action == null)
                  throw new NullPointerException();
              Node<K,V>[] tab = map.table;
              if (tab != null && tab.length >= (hi = getFence()) && index >= 0) {
                  while (current != null || index < hi) {
                      if (current == null)
                          current = tab[index++];
                      else {
                          V v = current.value;
                          current = current.next;
                          action.accept(v);
                          if (map.modCount != expectedModCount)
                              throw new ConcurrentModificationException();
                          return true;
                      }
                  }
              }
              return false;
          }
  
          public int characteristics() {
              return (fence < 0 || est == map.size ? Spliterator.SIZED : 0);
          }
      }
  
      static final class EntrySpliterator<K,V>
          extends HashMapSpliterator<K,V>
          implements Spliterator<Entry<K,V>> {
          EntrySpliterator(HashMap<K,V> m, int origin, int fence, int est,
                           int expectedModCount) {
              super(m, origin, fence, est, expectedModCount);
          }
  
          public EntrySpliterator<K,V> trySplit() {
              int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
              return (lo >= mid || current != null) ? null :
                  new EntrySpliterator<>(map, lo, index = mid, est >>>= 1,
                                            expectedModCount);
          }
  
          public void forEachRemaining(Consumer<? super Entry<K,V>> action) {
              int i, hi, mc;
              if (action == null)
                  throw new NullPointerException();
              HashMap<K,V> m = map;
              Node<K,V>[] tab = m.table;
              if ((hi = fence) < 0) {
                  mc = expectedModCount = m.modCount;
                  hi = fence = (tab == null) ? 0 : tab.length;
              }
              else
                  mc = expectedModCount;
              if (tab != null && tab.length >= hi &&
                  (i = index) >= 0 && (i < (index = hi) || current != null)) {
                  Node<K,V> p = current;
                  current = null;
                  do {
                      if (p == null)
                          p = tab[i++];
                      else {
                          action.accept(p);
                          p = p.next;
                      }
                  } while (p != null || i < hi);
                  if (m.modCount != mc)
                      throw new ConcurrentModificationException();
              }
          }
  
          public boolean tryAdvance(Consumer<? super Entry<K,V>> action) {
              int hi;
              if (action == null)
                  throw new NullPointerException();
              Node<K,V>[] tab = map.table;
              if (tab != null && tab.length >= (hi = getFence()) && index >= 0) {
                  while (current != null || index < hi) {
                      if (current == null)
                          current = tab[index++];
                      else {
                          Node<K,V> e = current;
                          current = current.next;
                          action.accept(e);
                          if (map.modCount != expectedModCount)
                              throw new ConcurrentModificationException();
                          return true;
                      }
                  }
              }
              return false;
          }
  
          public int characteristics() {
              return (fence < 0 || est == map.size ? Spliterator.SIZED : 0) |
                  Spliterator.DISTINCT;
          }
      }
  
      /* ------------------------------------------------------------ */
      // LinkedHashMap support
  
  
      /*
       * The following package-protected methods are designed to be
       * overridden by LinkedHashMap, but not by any other subclass.
       * Nearly all other internal methods are also package-protected
       * but are declared final, so can be used by LinkedHashMap, view
       * classes, and HashSet.
       */
  
      // Create a regular (non-tree) node
      Node<K,V> newNode(int hash, K key, V value, Node<K,V> next) {
          return new Node<>(hash, key, value, next);
      }
  
      // For conversion from TreeNodes to plain nodes
      Node<K,V> replacementNode(Node<K,V> p, Node<K,V> next) {
          return new Node<>(p.hash, p.key, p.value, next);
      }
  
      // Create a tree bin node
      TreeNode<K,V> newTreeNode(int hash, K key, V value, Node<K,V> next) {
          return new TreeNode<>(hash, key, value, next);
      }
  
      // For treeifyBin
      TreeNode<K,V> replacementTreeNode(Node<K,V> p, Node<K,V> next) {
          return new TreeNode<>(p.hash, p.key, p.value, next);
      }
  
      /**
       * Reset to initial default state.  Called by clone and readObject.
       */
      void reinitialize() {
          table = null;
          entrySet = null;
          keySet = null;
          values = null;
          modCount = 0;
          threshold = 0;
          size = 0;
      }
  
      // Callbacks to allow LinkedHashMap post-actions
      void afterNodeAccess(Node<K,V> p) { }
      void afterNodeInsertion(boolean evict) { }
      void afterNodeRemoval(Node<K,V> p) { }
  
      // Called only from writeObject, to ensure compatible ordering.
      void internalWriteEntries(java.io.ObjectOutputStream s) throws IOException {
          Node<K,V>[] tab;
          if (size > 0 && (tab = table) != null) {
              for (int i = 0; i < tab.length; ++i) {
                  for (Node<K,V> e = tab[i]; e != null; e = e.next) {
                      s.writeObject(e.key);
                      s.writeObject(e.value);
                  }
              }
          }
      }
  
      /* ------------------------------------------------------------ */
      // Tree bins
  
      /**
       * Entry for Tree bins. Extends LinkedHashMap.Entry (which in turn
       * extends Node) so can be used as extension of either regular or
       * linked node.
       */
      static final class TreeNode<K,V> extends LinkedHashMap.LinkedHashMapEntry<K,V> {
          TreeNode<K,V> parent;  // red-black tree links
          TreeNode<K,V> left;
          TreeNode<K,V> right;
          TreeNode<K,V> prev;    // needed to unlink next upon deletion
          boolean red;
          TreeNode(int hash, K key, V val, Node<K,V> next) {
              super(hash, key, val, next);
          }
  
          /**
           * Returns root of tree containing this node.
           */
          final TreeNode<K,V> root() {
              for (TreeNode<K,V> r = this, p;;) {
                  if ((p = r.parent) == null)
                      return r;
                  r = p;
              }
          }
  
          /**
           * Ensures that the given root is the first node of its bin.
           */
          static <K,V> void moveRootToFront(Node<K,V>[] tab, TreeNode<K,V> root) {
              int n;
              if (root != null && tab != null && (n = tab.length) > 0) {
                  int index = (n - 1) & root.hash;
                  TreeNode<K,V> first = (TreeNode<K,V>)tab[index];
                  if (root != first) {
                      Node<K,V> rn;
                      tab[index] = root;
                      TreeNode<K,V> rp = root.prev;
                      if ((rn = root.next) != null)
                          ((TreeNode<K,V>)rn).prev = rp;
                      if (rp != null)
                          rp.next = rn;
                      if (first != null)
                          first.prev = root;
                      root.next = first;
                      root.prev = null;
                  }
                  assert checkInvariants(root);
              }
          }
  
          /**
           * Finds the node starting at root p with the given hash and key.
           * The kc argument caches comparableClassFor(key) upon first use
           * comparing keys.
           */
          final TreeNode<K,V> find(int h, Object k, Class<?> kc) {
              TreeNode<K,V> p = this;
              do {
                  int ph, dir; K pk;
                  TreeNode<K,V> pl = p.left, pr = p.right, q;
                  if ((ph = p.hash) > h)
                      p = pl;
                  else if (ph < h)
                      p = pr;
                  else if ((pk = p.key) == k || (k != null && k.equals(pk)))
                      return p;
                  else if (pl == null)
                      p = pr;
                  else if (pr == null)
                      p = pl;
                  else if ((kc != null ||
                            (kc = comparableClassFor(k)) != null) &&
                           (dir = compareComparables(kc, k, pk)) != 0)
                      p = (dir < 0) ? pl : pr;
                  else if ((q = pr.find(h, k, kc)) != null)
                      return q;
                  else
                      p = pl;
              } while (p != null);
              return null;
          }
  
          /**
           * Calls find for root node.
           */
          final TreeNode<K,V> getTreeNode(int h, Object k) {
              return ((parent != null) ? root() : this).find(h, k, null);
          }
  
          /**
           * Tie-breaking utility for ordering insertions when equal
           * hashCodes and non-comparable. We don't require a total
           * order, just a consistent insertion rule to maintain
           * equivalence across rebalancings. Tie-breaking further than
           * necessary simplifies testing a bit.
           */
          static int tieBreakOrder(Object a, Object b) {
              int d;
              if (a == null || b == null ||
                  (d = a.getClass().getName().
                   compareTo(b.getClass().getName())) == 0)
                  d = (System.identityHashCode(a) <= System.identityHashCode(b) ?
                       -1 : 1);
              return d;
          }
  
          /**
           * Forms tree of the nodes linked from this node.
           * @return root of tree
           */
          final void treeify(Node<K,V>[] tab) {
              TreeNode<K,V> root = null;
              for (TreeNode<K,V> x = this, next; x != null; x = next) {
                  next = (TreeNode<K,V>)x.next;
                  x.left = x.right = null;
                  if (root == null) {
                      x.parent = null;
                      x.red = false;
                      root = x;
                  }
                  else {
                      K k = x.key;
                      int h = x.hash;
                      Class<?> kc = null;
                      for (TreeNode<K,V> p = root;;) {
                          int dir, ph;
                          K pk = p.key;
                          if ((ph = p.hash) > h)
                              dir = -1;
                          else if (ph < h)
                              dir = 1;
                          else if ((kc == null &&
                                    (kc = comparableClassFor(k)) == null) ||
                                   (dir = compareComparables(kc, k, pk)) == 0)
                              dir = tieBreakOrder(k, pk);
  
                          TreeNode<K,V> xp = p;
                          if ((p = (dir <= 0) ? p.left : p.right) == null) {
                              x.parent = xp;
                              if (dir <= 0)
                                  xp.left = x;
                              else
                                  xp.right = x;
                              root = balanceInsertion(root, x);
                              break;
                          }
                      }
                  }
              }
              moveRootToFront(tab, root);
          }
  
          /**
           * Returns a list of non-TreeNodes replacing those linked from
           * this node.
           */
          final Node<K,V> untreeify(HashMap<K,V> map) {
              Node<K,V> hd = null, tl = null;
              for (Node<K,V> q = this; q != null; q = q.next) {
                  Node<K,V> p = map.replacementNode(q, null);
                  if (tl == null)
                      hd = p;
                  else
                      tl.next = p;
                  tl = p;
              }
              return hd;
          }
  
          /**
           * Tree version of putVal.
           */
          final TreeNode<K,V> putTreeVal(HashMap<K,V> map, Node<K,V>[] tab,
                                         int h, K k, V v) {
              Class<?> kc = null;
              boolean searched = false;
              TreeNode<K,V> root = (parent != null) ? root() : this;
              for (TreeNode<K,V> p = root;;) {
                  int dir, ph; K pk;
                  if ((ph = p.hash) > h)
                      dir = -1;
                  else if (ph < h)
                      dir = 1;
                  else if ((pk = p.key) == k || (k != null && k.equals(pk)))
                      return p;
                  else if ((kc == null &&
                            (kc = comparableClassFor(k)) == null) ||
                           (dir = compareComparables(kc, k, pk)) == 0) {
                      if (!searched) {
                          TreeNode<K,V> q, ch;
                          searched = true;
                          if (((ch = p.left) != null &&
                               (q = ch.find(h, k, kc)) != null) ||
                              ((ch = p.right) != null &&
                               (q = ch.find(h, k, kc)) != null))
                              return q;
                      }
                      dir = tieBreakOrder(k, pk);
                  }
  
                  TreeNode<K,V> xp = p;
                  if ((p = (dir <= 0) ? p.left : p.right) == null) {
                      Node<K,V> xpn = xp.next;
                      TreeNode<K,V> x = map.newTreeNode(h, k, v, xpn);
                      if (dir <= 0)
                          xp.left = x;
                      else
                          xp.right = x;
                      xp.next = x;
                      x.parent = x.prev = xp;
                      if (xpn != null)
                          ((TreeNode<K,V>)xpn).prev = x;
                      moveRootToFront(tab, balanceInsertion(root, x));
                      return null;
                  }
              }
          }
  
          /**
           * Removes the given node, that must be present before this call.
           * This is messier than typical red-black deletion code because we
           * cannot swap the contents of an interior node with a leaf
           * successor that is pinned by "next" pointers that are accessible
           * independently during traversal. So instead we swap the tree
           * linkages. If the current tree appears to have too few nodes,
           * the bin is converted back to a plain bin. (The test triggers
           * somewhere between 2 and 6 nodes, depending on tree structure).
           */
          final void removeTreeNode(HashMap<K,V> map, Node<K,V>[] tab,
                                    boolean movable) {
              int n;
              if (tab == null || (n = tab.length) == 0)
                  return;
              int index = (n - 1) & hash;
              TreeNode<K,V> first = (TreeNode<K,V>)tab[index], root = first, rl;
              TreeNode<K,V> succ = (TreeNode<K,V>)next, pred = prev;
              if (pred == null)
                  tab[index] = first = succ;
              else
                  pred.next = succ;
              if (succ != null)
                  succ.prev = pred;
              if (first == null)
                  return;
              if (root.parent != null)
                  root = root.root();
              if (root == null || root.right == null ||
                  (rl = root.left) == null || rl.left == null) {
                  tab[index] = first.untreeify(map);  // too small
                  return;
              }
              TreeNode<K,V> p = this, pl = left, pr = right, replacement;
              if (pl != null && pr != null) {
                  TreeNode<K,V> s = pr, sl;
                  while ((sl = s.left) != null) // find successor
                      s = sl;
                  boolean c = s.red; s.red = p.red; p.red = c; // swap colors
                  TreeNode<K,V> sr = s.right;
                  TreeNode<K,V> pp = p.parent;
                  if (s == pr) { // p was s's direct parent
                      p.parent = s;
                      s.right = p;
                  }
                  else {
                      TreeNode<K,V> sp = s.parent;
                      if ((p.parent = sp) != null) {
                          if (s == sp.left)
                              sp.left = p;
                          else
                              sp.right = p;
                      }
                      if ((s.right = pr) != null)
                          pr.parent = s;
                  }
                  p.left = null;
                  if ((p.right = sr) != null)
                      sr.parent = p;
                  if ((s.left = pl) != null)
                      pl.parent = s;
                  if ((s.parent = pp) == null)
                      root = s;
                  else if (p == pp.left)
                      pp.left = s;
                  else
                      pp.right = s;
                  if (sr != null)
                      replacement = sr;
                  else
                      replacement = p;
              }
              else if (pl != null)
                  replacement = pl;
              else if (pr != null)
                  replacement = pr;
              else
                  replacement = p;
              if (replacement != p) {
                  TreeNode<K,V> pp = replacement.parent = p.parent;
                  if (pp == null)
                      root = replacement;
                  else if (p == pp.left)
                      pp.left = replacement;
                  else
                      pp.right = replacement;
                  p.left = p.right = p.parent = null;
              }
  
              TreeNode<K,V> r = p.red ? root : balanceDeletion(root, replacement);
  
              if (replacement == p) {  // detach
                  TreeNode<K,V> pp = p.parent;
                  p.parent = null;
                  if (pp != null) {
                      if (p == pp.left)
                          pp.left = null;
                      else if (p == pp.right)
                          pp.right = null;
                  }
              }
              if (movable)
                  moveRootToFront(tab, r);
          }
  
          /**
           * Splits nodes in a tree bin into lower and upper tree bins,
           * or untreeifies if now too small. Called only from resize;
           * see above discussion about split bits and indices.
           *
           * @param map the map
           * @param tab the table for recording bin heads
           * @param index the index of the table being split
           * @param bit the bit of hash to split on
           */
          final void split(HashMap<K,V> map, Node<K,V>[] tab, int index, int bit) {
              TreeNode<K,V> b = this;
              // Relink into lo and hi lists, preserving order
              TreeNode<K,V> loHead = null, loTail = null;
              TreeNode<K,V> hiHead = null, hiTail = null;
              int lc = 0, hc = 0;
              for (TreeNode<K,V> e = b, next; e != null; e = next) {
                  next = (TreeNode<K,V>)e.next;
                  e.next = null;
                  if ((e.hash & bit) == 0) {
                      if ((e.prev = loTail) == null)
                          loHead = e;
                      else
                          loTail.next = e;
                      loTail = e;
                      ++lc;
                  }
                  else {
                      if ((e.prev = hiTail) == null)
                          hiHead = e;
                      else
                          hiTail.next = e;
                      hiTail = e;
                      ++hc;
                  }
              }
  
              if (loHead != null) {
                  if (lc <= UNTREEIFY_THRESHOLD)
                      tab[index] = loHead.untreeify(map);
                  else {
                      tab[index] = loHead;
                      if (hiHead != null) // (else is already treeified)
                          loHead.treeify(tab);
                  }
              }
              if (hiHead != null) {
                  if (hc <= UNTREEIFY_THRESHOLD)
                      tab[index + bit] = hiHead.untreeify(map);
                  else {
                      tab[index + bit] = hiHead;
                      if (loHead != null)
                          hiHead.treeify(tab);
                  }
              }
          }
  
          /* ------------------------------------------------------------ */
          // Red-black tree methods, all adapted from CLR
  
          static <K,V> TreeNode<K,V> rotateLeft(TreeNode<K,V> root,
                                                TreeNode<K,V> p) {
              TreeNode<K,V> r, pp, rl;
              if (p != null && (r = p.right) != null) {
                  if ((rl = p.right = r.left) != null)
                      rl.parent = p;
                  if ((pp = r.parent = p.parent) == null)
                      (root = r).red = false;
                  else if (pp.left == p)
                      pp.left = r;
                  else
                      pp.right = r;
                  r.left = p;
                  p.parent = r;
              }
              return root;
          }
  
          static <K,V> TreeNode<K,V> rotateRight(TreeNode<K,V> root,
                                                 TreeNode<K,V> p) {
              TreeNode<K,V> l, pp, lr;
              if (p != null && (l = p.left) != null) {
                  if ((lr = p.left = l.right) != null)
                      lr.parent = p;
                  if ((pp = l.parent = p.parent) == null)
                      (root = l).red = false;
                  else if (pp.right == p)
                      pp.right = l;
                  else
                      pp.left = l;
                  l.right = p;
                  p.parent = l;
              }
              return root;
          }
  
          static <K,V> TreeNode<K,V> balanceInsertion(TreeNode<K,V> root,
                                                      TreeNode<K,V> x) {
              x.red = true;
              for (TreeNode<K,V> xp, xpp, xppl, xppr;;) {
                  if ((xp = x.parent) == null) {
                      x.red = false;
                      return x;
                  }
                  else if (!xp.red || (xpp = xp.parent) == null)
                      return root;
                  if (xp == (xppl = xpp.left)) {
                      if ((xppr = xpp.right) != null && xppr.red) {
                          xppr.red = false;
                          xp.red = false;
                          xpp.red = true;
                          x = xpp;
                      }
                      else {
                          if (x == xp.right) {
                              root = rotateLeft(root, x = xp);
                              xpp = (xp = x.parent) == null ? null : xp.parent;
                          }
                          if (xp != null) {
                              xp.red = false;
                              if (xpp != null) {
                                  xpp.red = true;
                                  root = rotateRight(root, xpp);
                              }
                          }
                      }
                  }
                  else {
                      if (xppl != null && xppl.red) {
                          xppl.red = false;
                          xp.red = false;
                          xpp.red = true;
                          x = xpp;
                      }
                      else {
                          if (x == xp.left) {
                              root = rotateRight(root, x = xp);
                              xpp = (xp = x.parent) == null ? null : xp.parent;
                          }
                          if (xp != null) {
                              xp.red = false;
                              if (xpp != null) {
                                  xpp.red = true;
                                  root = rotateLeft(root, xpp);
                              }
                          }
                      }
                  }
              }
          }
  
          static <K,V> TreeNode<K,V> balanceDeletion(TreeNode<K,V> root,
                                                     TreeNode<K,V> x) {
              for (TreeNode<K,V> xp, xpl, xpr;;)  {
                  if (x == null || x == root)
                      return root;
                  else if ((xp = x.parent) == null) {
                      x.red = false;
                      return x;
                  }
                  else if (x.red) {
                      x.red = false;
                      return root;
                  }
                  else if ((xpl = xp.left) == x) {
                      if ((xpr = xp.right) != null && xpr.red) {
                          xpr.red = false;
                          xp.red = true;
                          root = rotateLeft(root, xp);
                          xpr = (xp = x.parent) == null ? null : xp.right;
                      }
                      if (xpr == null)
                          x = xp;
                      else {
                          TreeNode<K,V> sl = xpr.left, sr = xpr.right;
                          if ((sr == null || !sr.red) &&
                              (sl == null || !sl.red)) {
                              xpr.red = true;
                              x = xp;
                          }
                          else {
                              if (sr == null || !sr.red) {
                                  if (sl != null)
                                      sl.red = false;
                                  xpr.red = true;
                                  root = rotateRight(root, xpr);
                                  xpr = (xp = x.parent) == null ?
                                      null : xp.right;
                              }
                              if (xpr != null) {
                                  xpr.red = (xp == null) ? false : xp.red;
                                  if ((sr = xpr.right) != null)
                                      sr.red = false;
                              }
                              if (xp != null) {
                                  xp.red = false;
                                  root = rotateLeft(root, xp);
                              }
                              x = root;
                          }
                      }
                  }
                  else { // symmetric
                      if (xpl != null && xpl.red) {
                          xpl.red = false;
                          xp.red = true;
                          root = rotateRight(root, xp);
                          xpl = (xp = x.parent) == null ? null : xp.left;
                      }
                      if (xpl == null)
                          x = xp;
                      else {
                          TreeNode<K,V> sl = xpl.left, sr = xpl.right;
                          if ((sl == null || !sl.red) &&
                              (sr == null || !sr.red)) {
                              xpl.red = true;
                              x = xp;
                          }
                          else {
                              if (sl == null || !sl.red) {
                                  if (sr != null)
                                      sr.red = false;
                                  xpl.red = true;
                                  root = rotateLeft(root, xpl);
                                  xpl = (xp = x.parent) == null ?
                                      null : xp.left;
                              }
                              if (xpl != null) {
                                  xpl.red = (xp == null) ? false : xp.red;
                                  if ((sl = xpl.left) != null)
                                      sl.red = false;
                              }
                              if (xp != null) {
                                  xp.red = false;
                                  root = rotateRight(root, xp);
                              }
                              x = root;
                          }
                      }
                  }
              }
          }
  
          /**
           * Recursive invariant check
           */
          static <K,V> boolean checkInvariants(TreeNode<K,V> t) {
              TreeNode<K,V> tp = t.parent, tl = t.left, tr = t.right,
                  tb = t.prev, tn = (TreeNode<K,V>)t.next;
              if (tb != null && tb.next != t)
                  return false;
              if (tn != null && tn.prev != t)
                  return false;
              if (tp != null && t != tp.left && t != tp.right)
                  return false;
              if (tl != null && (tl.parent != t || tl.hash > t.hash))
                  return false;
              if (tr != null && (tr.parent != t || tr.hash < t.hash))
                  return false;
              if (t.red && tl != null && tl.red && tr != null && tr.red)
                  return false;
              if (tl != null && !checkInvariants(tl))
                  return false;
              if (tr != null && !checkInvariants(tr))
                  return false;
              return true;
          }
      }
  
  }
  