Java example source code file (ForwardingImmutableMap.java)

This example Java source code file (ForwardingImmutableMap.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, classcastexception, entry, forwardingimmutablemap, forwardingset, illegalargumentexception, immutablecollection, immutableset, object, override, string, suppresswarnings, util

The ForwardingImmutableMap.java Java example source code

/*
 * Copyright (C) 2009 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 java.util.Collections;
import java.util.Map;
import java.util.Set;

import javax.annotation.Nullable;

/**
 * GWT implementation of {@link ImmutableMap} that forwards to another map.
 *
 * @author Hayward Chan
 */
public abstract class ForwardingImmutableMap<K, V> extends ImmutableMap {

  final transient Map<K, V> delegate;

  ForwardingImmutableMap(Map<? extends K, ? extends V> delegate) {
    this.delegate = Collections.unmodifiableMap(delegate);
  }

  @SuppressWarnings("unchecked")
  ForwardingImmutableMap(Entry<? extends K, ? extends V>... entries) {
    Map<K, V> delegate = Maps.newLinkedHashMap();
    for (Entry<? extends K, ? extends V> entry : entries) {
      K key = checkNotNull(entry.getKey());
      V previous = delegate.put(key, checkNotNull(entry.getValue()));
      if (previous != null) {
        throw new IllegalArgumentException("duplicate key: " + key);
      }
    }
    this.delegate = Collections.unmodifiableMap(delegate);
  }

  boolean isPartialView() {
    return false;
  }

  public final boolean isEmpty() {
    return delegate.isEmpty();
  }

  public final boolean containsKey(@Nullable Object key) {
    return Maps.safeContainsKey(delegate, key);
  }

  public final boolean containsValue(@Nullable Object value) {
    return delegate.containsValue(value);
  }

  public V get(@Nullable Object key) {
    return (key == null) ? null : Maps.safeGet(delegate, key);
  }

  @Override ImmutableSet<Entry createEntrySet() {
    return ImmutableSet.unsafeDelegate(
        new ForwardingSet<Entry() {
          @Override protected Set<Entry delegate() {
            return delegate.entrySet();
          }
          @Override public boolean contains(Object object) {
            if (object instanceof Entry<?, ?>
                && ((Entry<?, ?>) object).getKey() == null) {
              return false;
            }
            try {
              return super.contains(object);
            } catch (ClassCastException e) {
              return false;
            }
          }
          @Override public <T> T[] toArray(T[] array) {
            T[] result = super.toArray(array);
            if (size() < result.length) {
              // It works around a GWT bug where elements after last is not
              // properly null'ed.
              result[size()] = null;
            }
            return result;
          }
        });
  }

  @Override ImmutableSet<K> createKeySet() {
    return ImmutableSet.unsafeDelegate(delegate.keySet());
  }

  @Override ImmutableCollection<V> createValues() {
    return ImmutableCollection.unsafeDelegate(delegate.values());
  }

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

  @Override public boolean equals(@Nullable Object object) {
    return delegate.equals(object);
  }

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

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