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Java example source code file (RegularImmutableMultiset.java)

This example Java source code file (RegularImmutableMultiset.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

annotation, elementset, empty, gwtcompatible, immutableentry, immutableset, nonterminalentry, object, override, regularimmutablemultiset, suppresswarnings, util, weakouter

The RegularImmutableMultiset.java Java example source code

/*
 * Copyright (C) 2011 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 static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Objects;
import com.google.common.collect.Multisets.ImmutableEntry;
import com.google.common.primitives.Ints;
import com.google.j2objc.annotations.WeakOuter;

import java.util.Collection;

import javax.annotation.Nullable;

/**
 * Implementation of {@link ImmutableMultiset} with zero or more elements.
 *
 * @author Jared Levy
 * @author Louis Wasserman
 */
@GwtCompatible(serializable = true)
@SuppressWarnings("serial") // uses writeReplace(), not default serialization
class RegularImmutableMultiset<E> extends ImmutableMultiset {
  static final RegularImmutableMultiset<Object> EMPTY =
      new RegularImmutableMultiset<Object>(ImmutableList.>of());

  private final transient Multisets.ImmutableEntry<E>[] entries;
  private final transient Multisets.ImmutableEntry<E>[] hashTable;
  private final transient int size;
  private final transient int hashCode;

  private transient ImmutableSet<E> elementSet;

  RegularImmutableMultiset(Collection<? extends Entry entries) {
    int distinct = entries.size();
    @SuppressWarnings("unchecked")
    Multisets.ImmutableEntry<E>[] entryArray = new Multisets.ImmutableEntry[distinct];
    if (distinct == 0) {
      this.entries = entryArray;
      this.hashTable = null;
      this.size = 0;
      this.hashCode = 0;
      this.elementSet = ImmutableSet.of();
    } else {
      int tableSize = Hashing.closedTableSize(distinct, 1.0);
      int mask = tableSize - 1;
      @SuppressWarnings("unchecked")
      Multisets.ImmutableEntry<E>[] hashTable = new Multisets.ImmutableEntry[tableSize];

      int index = 0;
      int hashCode = 0;
      long size = 0;
      for (Entry<? extends E> entry : entries) {
        E element = checkNotNull(entry.getElement());
        int count = entry.getCount();
        int hash = element.hashCode();
        int bucket = Hashing.smear(hash) & mask;
        Multisets.ImmutableEntry<E> bucketHead = hashTable[bucket];
        Multisets.ImmutableEntry<E> newEntry;
        if (bucketHead == null) {
          boolean canReuseEntry =
              entry instanceof Multisets.ImmutableEntry && !(entry instanceof NonTerminalEntry);
          newEntry =
              canReuseEntry
                  ? (Multisets.ImmutableEntry<E>) entry
                  : new Multisets.ImmutableEntry<E>(element, count);
        } else {
          newEntry = new NonTerminalEntry<E>(element, count, bucketHead);
        }
        hashCode += hash ^ count;
        entryArray[index++] = newEntry;
        hashTable[bucket] = newEntry;
        size += count;
      }
      this.entries = entryArray;
      this.hashTable = hashTable;
      this.size = Ints.saturatedCast(size);
      this.hashCode = hashCode;
    }
  }

  private static final class NonTerminalEntry<E> extends Multisets.ImmutableEntry {
    private final Multisets.ImmutableEntry<E> nextInBucket;

    NonTerminalEntry(E element, int count, ImmutableEntry<E> nextInBucket) {
      super(element, count);
      this.nextInBucket = nextInBucket;
    }

    @Override
    public ImmutableEntry<E> nextInBucket() {
      return nextInBucket;
    }
  }

  @Override
  boolean isPartialView() {
    return false;
  }

  @Override
  public int count(@Nullable Object element) {
    Multisets.ImmutableEntry<E>[] hashTable = this.hashTable;
    if (element == null || hashTable == null) {
      return 0;
    }
    int hash = Hashing.smearedHash(element);
    int mask = hashTable.length - 1;
    for (Multisets.ImmutableEntry<E> entry = hashTable[hash & mask];
        entry != null;
        entry = entry.nextInBucket()) {
      if (Objects.equal(element, entry.getElement())) {
        return entry.getCount();
      }
    }
    return 0;
  }

  @Override
  public int size() {
    return size;
  }

  @Override
  public ImmutableSet<E> elementSet() {
    ImmutableSet<E> result = elementSet;
    return (result == null) ? elementSet = new ElementSet() : result;
  }

  @WeakOuter
  private final class ElementSet extends ImmutableSet.Indexed<E> {

    @Override
    E get(int index) {
      return entries[index].getElement();
    }

    @Override
    public boolean contains(@Nullable Object object) {
      return RegularImmutableMultiset.this.contains(object);
    }

    @Override
    boolean isPartialView() {
      return true;
    }

    @Override
    public int size() {
      return entries.length;
    }
  }

  @Override
  Entry<E> getEntry(int index) {
    return entries[index];
  }

  @Override
  public int hashCode() {
    return hashCode;
  }
}

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