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Java example source code file (DescendingMultiset.java)

This example Java source code file (DescendingMultiset.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

boundtype, comparator, descendingmultiset, entry, entrysetimpl, gwtcompatible, iterator, navigableset, object, override, sortedmultiset, string, util, weakouter

The DescendingMultiset.java Java example source code

/*
 * Copyright (C) 2012 The Guava Authors
 *
 * Licensed 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 com.google.common.collect;

import com.google.common.annotations.GwtCompatible;
import com.google.j2objc.annotations.WeakOuter;

import java.util.Comparator;
import java.util.Iterator;
import java.util.NavigableSet;
import java.util.Set;

/**
 * A skeleton implementation of a descending multiset.  Only needs
 * {@code forwardMultiset()} and {@code entryIterator()}.
 *
 * @author Louis Wasserman
 */
@GwtCompatible(emulated = true)
abstract class DescendingMultiset<E> extends ForwardingMultiset implements SortedMultiset {
  abstract SortedMultiset<E> forwardMultiset();

  private transient Comparator<? super E> comparator;

  @Override
  public Comparator<? super E> comparator() {
    Comparator<? super E> result = comparator;
    if (result == null) {
      return comparator = Ordering.from(forwardMultiset().comparator()).<E>reverse();
    }
    return result;
  }

  private transient NavigableSet<E> elementSet;

  @Override
  public NavigableSet<E> elementSet() {
    NavigableSet<E> result = elementSet;
    if (result == null) {
      return elementSet = new SortedMultisets.NavigableElementSet<E>(this);
    }
    return result;
  }

  @Override
  public Entry<E> pollFirstEntry() {
    return forwardMultiset().pollLastEntry();
  }

  @Override
  public Entry<E> pollLastEntry() {
    return forwardMultiset().pollFirstEntry();
  }

  @Override
  public SortedMultiset<E> headMultiset(E toElement, BoundType boundType) {
    return forwardMultiset().tailMultiset(toElement, boundType).descendingMultiset();
  }

  @Override
  public SortedMultiset<E> subMultiset(
      E fromElement, BoundType fromBoundType, E toElement, BoundType toBoundType) {
    return forwardMultiset()
        .subMultiset(toElement, toBoundType, fromElement, fromBoundType)
        .descendingMultiset();
  }

  @Override
  public SortedMultiset<E> tailMultiset(E fromElement, BoundType boundType) {
    return forwardMultiset().headMultiset(fromElement, boundType).descendingMultiset();
  }

  @Override
  protected Multiset<E> delegate() {
    return forwardMultiset();
  }

  @Override
  public SortedMultiset<E> descendingMultiset() {
    return forwardMultiset();
  }

  @Override
  public Entry<E> firstEntry() {
    return forwardMultiset().lastEntry();
  }

  @Override
  public Entry<E> lastEntry() {
    return forwardMultiset().firstEntry();
  }

  abstract Iterator<Entry entryIterator();

  private transient Set<Entry entrySet;

  @Override
  public Set<Entry entrySet() {
    Set<Entry result = entrySet;
    return (result == null) ? entrySet = createEntrySet() : result;
  }

  Set<Entry createEntrySet() {
    @WeakOuter
    class EntrySetImpl extends Multisets.EntrySet<E> {
      @Override
      Multiset<E> multiset() {
        return DescendingMultiset.this;
      }

      @Override
      public Iterator<Entry iterator() {
        return entryIterator();
      }

      @Override
      public int size() {
        return forwardMultiset().entrySet().size();
      }
    }
    return new EntrySetImpl();
  }

  @Override
  public Iterator<E> iterator() {
    return Multisets.iteratorImpl(this);
  }

  @Override
  public Object[] toArray() {
    return standardToArray();
  }

  @Override
  public <T> T[] toArray(T[] array) {
    return standardToArray(array);
  }

  @Override
  public String toString() {
    return entrySet().toString();
  }
}

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