content: package org.apache.lucene.search;
  
  /**
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  import java.io.Serializable;
  import java.util.Arrays;
  
  
  /**
   * Encapsulates sort criteria for returned hits.
   *
   * <p>The fields used to determine sort order must be carefully chosen.
   * Documents must contain a single term in such a field,
   * and the value of the term should indicate the document's relative position in
   * a given sort order.  The field must be indexed, but should not be tokenized,
   * and does not need to be stored (unless you happen to want it back with the
   * rest of your document data).  In other words:
   *
   * <p><code>document.add (new Field ("byNumber", Integer.toString(x), Field.Store.NO, Field.Index.NOT_ANALYZED));</code></p>
   * 
   *
   * <p><h3>Valid Types of Values</h3>
   *
   * <p>There are four possible kinds of term values which may be put into
   * sorting fields: Integers, Longs, Floats, or Strings.  Unless
   * {@link SortField SortField} objects are specified, the type of value
   * in the field is determined by parsing the first term in the field.
   *
   * <p>Integer term values should contain only digits and an optional
   * preceding negative sign.  Values must be base 10 and in the range
   * <code>Integer.MIN_VALUE</code> and <code>Integer.MAX_VALUE</code> inclusive.
   * Documents which should appear first in the sort
   * should have low value integers, later documents high values
   * (i.e. the documents should be numbered <code>1..n</code> where
   * <code>1</code> is the first and <code>n</code> the last).
   *
   * <p>Long term values should contain only digits and an optional
   * preceding negative sign.  Values must be base 10 and in the range
   * <code>Long.MIN_VALUE</code> and <code>Long.MAX_VALUE</code> inclusive.
   * Documents which should appear first in the sort
   * should have low value integers, later documents high values.
   * 
   * <p>Float term values should conform to values accepted by
   * {@link Float Float.valueOf(String)} (except that <code>NaN</code>
   * and <code>Infinity</code> are not supported).
   * Documents which should appear first in the sort
   * should have low values, later documents high values.
   *
   * <p>String term values can contain any valid String, but should
   * not be tokenized.  The values are sorted according to their
   * {@link Comparable natural order}.  Note that using this type
   * of term value has higher memory requirements than the other
   * two types.
   *
   * <p><h3>Object Reuse</h3>
   *
   * <p>One of these objects can be
   * used multiple times and the sort order changed between usages.
   *
   * <p>This class is thread safe.
   *
   * <p><h3>Memory Usage</h3>
   *
   * <p>Sorting uses of caches of term values maintained by the
   * internal HitQueue(s).  The cache is static and contains an integer
   * or float array of length <code>IndexReader.maxDoc()</code> for each field
   * name for which a sort is performed.  In other words, the size of the
   * cache in bytes is:
   *
   * <p><code>4 * IndexReader.maxDoc() * (# of different fields actually used to sort)</code>
   *
   * <p>For String fields, the cache is larger: in addition to the
   * above array, the value of every term in the field is kept in memory.
   * If there are many unique terms in the field, this could
   * be quite large.
   *
   * <p>Note that the size of the cache is not affected by how many
   * fields are in the index and <i>might</i> be used to sort - only by
   * the ones actually used to sort a result set.
   *
   * <p>Created: Feb 12, 2004 10:53:57 AM
   *
   * @since   lucene 1.4
   */
  public class Sort
  implements Serializable {
  
    /**
     * Represents sorting by computed relevance. Using this sort criteria returns
     * the same results as calling
     * {@link Searcher#search(Query,int) Searcher#search()}without a sort criteria,
     * only with slightly more overhead.
     */
    public static final Sort RELEVANCE = new Sort();
  
    /** Represents sorting by index order. */
    public static final Sort INDEXORDER = new Sort(SortField.FIELD_DOC);
  
    // internal representation of the sort criteria
    SortField[] fields;
  
    /**
     * Sorts by computed relevance. This is the same sort criteria as calling
     * {@link Searcher#search(Query,int) Searcher#search()}without a sort criteria,
     * only with slightly more overhead.
     */
    public Sort() {
      this(SortField.FIELD_SCORE);
    }
  
    /** Sorts by the criteria in the given SortField. */
    public Sort(SortField field) {
      setSort(field);
    }
  
    /** Sorts in succession by the criteria in each SortField. */
    public Sort(SortField... fields) {
      setSort(fields);
    }
  
    /** Sets the sort to the given criteria. */
    public void setSort(SortField field) {
      this.fields = new SortField[] { field };
    }
  
    /** Sets the sort to the given criteria in succession. */
    public void setSort(SortField... fields) {
      this.fields = fields;
    }
    
    /**
     * Representation of the sort criteria.
     * @return Array of SortField objects used in this sort criteria
     */
    public SortField[] getSort() {
      return fields;
    }
  
    @Override
    public String toString() {
      StringBuilder buffer = new StringBuilder();
  
      for (int i = 0; i < fields.length; i++) {
        buffer.append(fields[i].toString());
        if ((i+1) < fields.length)
          buffer.append(',');
      }
  
      return buffer.toString();
    }
  
    /** Returns true if <code>o</code> is equal to this. */
    @Override
    public boolean equals(Object o) {
      if (this == o) return true;
      if (!(o instanceof Sort)) return false;
      final Sort other = (Sort)o;
      return Arrays.equals(this.fields, other.fields);
    }
  
    /** Returns a hash code value for this object. */
    @Override
    public int hashCode() {
      return 0x45aaf665 + Arrays.hashCode(fields);
    }
  }
  