content: /*
   * 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.
   */
  
  package org.apache.bookkeeper.common.util;
  
  import java.util.Iterator;
  import java.util.Objects;
  import java.util.Spliterator;
  import java.util.Spliterators;
  import java.util.function.BiFunction;
  import java.util.stream.Stream;
  import java.util.stream.StreamSupport;
  
  /**
   * Java {@link java.util.stream.Stream} related operations.
   */
  public class StreamUtil {
  
      public static <T1, T2, R> Stream<R> zip(Stream<? extends T1> a,
                                              Stream<? extends T2> b,
                                              BiFunction<? super T1, ? super T2, ? extends R> zipper) {
          Objects.requireNonNull(zipper);
          Spliterator<? extends T1> aSpliterator = Objects.requireNonNull(a).spliterator();
          Spliterator<? extends T2> bSpliterator = Objects.requireNonNull(b).spliterator();
  
          // Zipping looses DISTINCT and SORTED characteristics
          int characteristics = aSpliterator.characteristics() & bSpliterator.characteristics()
              & ~(Spliterator.DISTINCT | Spliterator.SORTED);
  
          long zipSize = ((characteristics & Spliterator.SIZED) != 0)
              ? Math.min(aSpliterator.getExactSizeIfKnown(), bSpliterator.getExactSizeIfKnown())
              : -1;
  
          Iterator<T1> aIterator = Spliterators.iterator(aSpliterator);
          Iterator<T2> bIterator = Spliterators.iterator(bSpliterator);
          Iterator<R> cIterator = new Iterator<R>() {
              @Override
              public boolean hasNext() {
                  return aIterator.hasNext() && bIterator.hasNext();
              }
  
              @Override
              public R next() {
                  return zipper.apply(aIterator.next(), bIterator.next());
              }
          };
  
          Spliterator<R> split = Spliterators.spliterator(cIterator, zipSize, characteristics);
          return (a.isParallel() || b.isParallel())
              ? StreamSupport.stream(split, true)
              : StreamSupport.stream(split, false);
      }
  
  
  }
  