Update #0 - First Release

sources/main/java/com/google/common/collect/ForwardingMap.java

@@ -0,0 +1,319 @@
+/*
+ * Copyright (C) 2007 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 java.util.Collection;
+import java.util.Iterator;
+import java.util.Map;
+import java.util.Set;
+
+import javax.annotation.Nullable;
+
+import com.google.common.annotations.Beta;
+import com.google.common.annotations.GwtCompatible;
+import com.google.common.base.Objects;
+
+/**
+ * A map which forwards all its method calls to another map. Subclasses should
+ * override one or more methods to modify the behavior of the backing map as
+ * desired per the
+ * <a href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator
+ * pattern</a>.
+ *
+ * <p>
+ * <i>Warning:</i> The methods of {@code ForwardingMap} forward
+ * <i>indiscriminately</i> to the methods of the delegate. For example,
+ * overriding {@link #put} alone <i>will not</i> change the behavior of
+ * {@link #putAll}, which can lead to unexpected behavior. In this case, you
+ * should override {@code putAll} as well, either providing your own
+ * implementation, or delegating to the provided {@code standardPutAll} method.
+ *
+ * <p>
+ * Each of the {@code standard} methods, where appropriate, use
+ * {@link Objects#equal} to test equality for both keys and values. This may not
+ * be the desired behavior for map implementations that use non-standard notions
+ * of key equality, such as a {@code SortedMap} whose comparator is not
+ * consistent with {@code equals}.
+ *
+ * <p>
+ * The {@code standard} methods and the collection views they return are not
+ * guaranteed to be thread-safe, even when all of the methods that they depend
+ * on are thread-safe.
+ *
+ * @author Kevin Bourrillion
+ * @author Jared Levy
+ * @author Louis Wasserman
+ * @since 2.0 (imported from Google Collections Library)
+ */
+@GwtCompatible
+public abstract class ForwardingMap<K, V> extends ForwardingObject implements Map<K, V> {
+	// TODO(user): identify places where thread safety is actually lost
+
+	/** Constructor for use by subclasses. */
+	protected ForwardingMap() {
+	}
+
+	@Override
+	protected abstract Map<K, V> delegate();
+
+	@Override
+	public int size() {
+		return delegate().size();
+	}
+
+	@Override
+	public boolean isEmpty() {
+		return delegate().isEmpty();
+	}
+
+	@Override
+	public V remove(Object object) {
+		return delegate().remove(object);
+	}
+
+	@Override
+	public void clear() {
+		delegate().clear();
+	}
+
+	@Override
+	public boolean containsKey(@Nullable Object key) {
+		return delegate().containsKey(key);
+	}
+
+	@Override
+	public boolean containsValue(@Nullable Object value) {
+		return delegate().containsValue(value);
+	}
+
+	@Override
+	public V get(@Nullable Object key) {
+		return delegate().get(key);
+	}
+
+	@Override
+	public V put(K key, V value) {
+		return delegate().put(key, value);
+	}
+
+	@Override
+	public void putAll(Map<? extends K, ? extends V> map) {
+		delegate().putAll(map);
+	}
+
+	@Override
+	public Set<K> keySet() {
+		return delegate().keySet();
+	}
+
+	@Override
+	public Collection<V> values() {
+		return delegate().values();
+	}
+
+	@Override
+	public Set<Entry<K, V>> entrySet() {
+		return delegate().entrySet();
+	}
+
+	@Override
+	public boolean equals(@Nullable Object object) {
+		return object == this || delegate().equals(object);
+	}
+
+	@Override
+	public int hashCode() {
+		return delegate().hashCode();
+	}
+
+	/**
+	 * A sensible definition of {@link #putAll(Map)} in terms of
+	 * {@link #put(Object, Object)}. If you override {@link #put(Object, Object)},
+	 * you may wish to override {@link #putAll(Map)} to forward to this
+	 * implementation.
+	 *
+	 * @since 7.0
+	 */
+	protected void standardPutAll(Map<? extends K, ? extends V> map) {
+		Maps.putAllImpl(this, map);
+	}
+
+	/**
+	 * A sensible, albeit inefficient, definition of {@link #remove} in terms of the
+	 * {@code iterator} method of {@link #entrySet}. If you override
+	 * {@link #entrySet}, you may wish to override {@link #remove} to forward to
+	 * this implementation.
+	 *
+	 * <p>
+	 * Alternately, you may wish to override {@link #remove} with {@code
+	 * keySet().remove}, assuming that approach would not lead to an infinite loop.
+	 *
+	 * @since 7.0
+	 */
+	@Beta
+	protected V standardRemove(@Nullable Object key) {
+		Iterator<Entry<K, V>> entryIterator = entrySet().iterator();
+		while (entryIterator.hasNext()) {
+			Entry<K, V> entry = entryIterator.next();
+			if (Objects.equal(entry.getKey(), key)) {
+				V value = entry.getValue();
+				entryIterator.remove();
+				return value;
+			}
+		}
+		return null;
+	}
+
+	/**
+	 * A sensible definition of {@link #clear} in terms of the {@code iterator}
+	 * method of {@link #entrySet}. In many cases, you may wish to override
+	 * {@link #clear} to forward to this implementation.
+	 *
+	 * @since 7.0
+	 */
+	protected void standardClear() {
+		Iterators.clear(entrySet().iterator());
+	}
+
+	/**
+	 * A sensible implementation of {@link Map#keySet} in terms of the following
+	 * methods: {@link ForwardingMap#clear}, {@link ForwardingMap#containsKey},
+	 * {@link ForwardingMap#isEmpty}, {@link ForwardingMap#remove},
+	 * {@link ForwardingMap#size}, and the {@link Set#iterator} method of
+	 * {@link ForwardingMap#entrySet}. In many cases, you may wish to override
+	 * {@link ForwardingMap#keySet} to forward to this implementation or a subclass
+	 * thereof.
+	 *
+	 * @since 10.0
+	 */
+	@Beta
+	protected class StandardKeySet extends Maps.KeySet<K, V> {
+		/** Constructor for use by subclasses. */
+		public StandardKeySet() {
+			super(ForwardingMap.this);
+		}
+	}
+
+	/**
+	 * A sensible, albeit inefficient, definition of {@link #containsKey} in terms
+	 * of the {@code iterator} method of {@link #entrySet}. If you override
+	 * {@link #entrySet}, you may wish to override {@link #containsKey} to forward
+	 * to this implementation.
+	 *
+	 * @since 7.0
+	 */
+	@Beta
+	protected boolean standardContainsKey(@Nullable Object key) {
+		return Maps.containsKeyImpl(this, key);
+	}
+
+	/**
+	 * A sensible implementation of {@link Map#values} in terms of the following
+	 * methods: {@link ForwardingMap#clear}, {@link ForwardingMap#containsValue},
+	 * {@link ForwardingMap#isEmpty}, {@link ForwardingMap#size}, and the
+	 * {@link Set#iterator} method of {@link ForwardingMap#entrySet}. In many cases,
+	 * you may wish to override {@link ForwardingMap#values} to forward to this
+	 * implementation or a subclass thereof.
+	 *
+	 * @since 10.0
+	 */
+	@Beta
+	protected class StandardValues extends Maps.Values<K, V> {
+		/** Constructor for use by subclasses. */
+		public StandardValues() {
+			super(ForwardingMap.this);
+		}
+	}
+
+	/**
+	 * A sensible definition of {@link #containsValue} in terms of the {@code
+	 * iterator} method of {@link #entrySet}. If you override {@link #entrySet}, you
+	 * may wish to override {@link #containsValue} to forward to this
+	 * implementation.
+	 *
+	 * @since 7.0
+	 */
+	protected boolean standardContainsValue(@Nullable Object value) {
+		return Maps.containsValueImpl(this, value);
+	}
+
+	/**
+	 * A sensible implementation of {@link Map#entrySet} in terms of the following
+	 * methods: {@link ForwardingMap#clear}, {@link ForwardingMap#containsKey},
+	 * {@link ForwardingMap#get}, {@link ForwardingMap#isEmpty},
+	 * {@link ForwardingMap#remove}, and {@link ForwardingMap#size}. In many cases,
+	 * you may wish to override {@link #entrySet} to forward to this implementation
+	 * or a subclass thereof.
+	 *
+	 * @since 10.0
+	 */
+	@Beta
+	protected abstract class StandardEntrySet extends Maps.EntrySet<K, V> {
+		/** Constructor for use by subclasses. */
+		public StandardEntrySet() {
+		}
+
+		@Override
+		Map<K, V> map() {
+			return ForwardingMap.this;
+		}
+	}
+
+	/**
+	 * A sensible definition of {@link #isEmpty} in terms of the {@code iterator}
+	 * method of {@link #entrySet}. If you override {@link #entrySet}, you may wish
+	 * to override {@link #isEmpty} to forward to this implementation.
+	 *
+	 * @since 7.0
+	 */
+	protected boolean standardIsEmpty() {
+		return !entrySet().iterator().hasNext();
+	}
+
+	/**
+	 * A sensible definition of {@link #equals} in terms of the {@code equals}
+	 * method of {@link #entrySet}. If you override {@link #entrySet}, you may wish
+	 * to override {@link #equals} to forward to this implementation.
+	 *
+	 * @since 7.0
+	 */
+	protected boolean standardEquals(@Nullable Object object) {
+		return Maps.equalsImpl(this, object);
+	}
+
+	/**
+	 * A sensible definition of {@link #hashCode} in terms of the {@code iterator}
+	 * method of {@link #entrySet}. If you override {@link #entrySet}, you may wish
+	 * to override {@link #hashCode} to forward to this implementation.
+	 *
+	 * @since 7.0
+	 */
+	protected int standardHashCode() {
+		return Sets.hashCodeImpl(entrySet());
+	}
+
+	/**
+	 * A sensible definition of {@link #toString} in terms of the {@code iterator}
+	 * method of {@link #entrySet}. If you override {@link #entrySet}, you may wish
+	 * to override {@link #toString} to forward to this implementation.
+	 *
+	 * @since 7.0
+	 */
+	protected String standardToString() {
+		return Maps.toStringImpl(this);
+	}
+}