EaglerForge/sources/main/java/com/google/common/collect/ImmutableEnumMap.java

/*
 * 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 static com.google.common.base.Preconditions.checkArgument;

import java.io.Serializable;
import java.util.EnumMap;
import java.util.Iterator;

import javax.annotation.Nullable;

import com.google.common.annotations.GwtCompatible;

/**
 * Implementation of {@link ImmutableMap} backed by a non-empty
 * {@link java.util.EnumMap}.
 *
 * @author Louis Wasserman
 */
@GwtCompatible(serializable = true, emulated = true)
@SuppressWarnings("serial") // we're overriding default serialization
final class ImmutableEnumMap<K extends Enum<K>, V> extends ImmutableMap<K, V> {
	static <K extends Enum<K>, V> ImmutableMap<K, V> asImmutable(EnumMap<K, V> map) {
		switch (map.size()) {
		case 0:
			return ImmutableMap.of();
		case 1: {
			Entry<K, V> entry = Iterables.getOnlyElement(map.entrySet());
			return ImmutableMap.of(entry.getKey(), entry.getValue());
		}
		default:
			return new ImmutableEnumMap<K, V>(map);
		}
	}

	private transient final EnumMap<K, V> delegate;

	private ImmutableEnumMap(EnumMap<K, V> delegate) {
		this.delegate = delegate;
		checkArgument(!delegate.isEmpty());
	}

	@Override
	ImmutableSet<K> createKeySet() {
		return new ImmutableSet<K>() {

			@Override
			public boolean contains(Object object) {
				return delegate.containsKey(object);
			}

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

			@Override
			public UnmodifiableIterator<K> iterator() {
				return Iterators.unmodifiableIterator(delegate.keySet().iterator());
			}

			@Override
			boolean isPartialView() {
				return true;
			}
		};
	}

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

	@Override
	public boolean containsKey(@Nullable Object key) {
		return delegate.containsKey(key);
	}

	@Override
	public V get(Object key) {
		return delegate.get(key);
	}

	@Override
	ImmutableSet<Entry<K, V>> createEntrySet() {
		return new ImmutableMapEntrySet<K, V>() {

			@Override
			ImmutableMap<K, V> map() {
				return ImmutableEnumMap.this;
			}

			@Override
			public UnmodifiableIterator<Entry<K, V>> iterator() {
				return new UnmodifiableIterator<Entry<K, V>>() {
					private final Iterator<Entry<K, V>> backingIterator = delegate.entrySet().iterator();

					@Override
					public boolean hasNext() {
						return backingIterator.hasNext();
					}

					@Override
					public Entry<K, V> next() {
						Entry<K, V> entry = backingIterator.next();
						return Maps.immutableEntry(entry.getKey(), entry.getValue());
					}
				};
			}
		};
	}

	@Override
	boolean isPartialView() {
		return false;
	}

	// All callers of the constructor are restricted to <K extends Enum<K>>.
	@Override
	Object writeReplace() {
		return new EnumSerializedForm<K, V>(delegate);
	}

	/*
	 * This class is used to serialize ImmutableEnumSet instances.
	 */
	private static class EnumSerializedForm<K extends Enum<K>, V> implements Serializable {
		final EnumMap<K, V> delegate;

		EnumSerializedForm(EnumMap<K, V> delegate) {
			this.delegate = delegate;
		}

		Object readResolve() {
			return new ImmutableEnumMap<K, V>(delegate);
		}

		private static final long serialVersionUID = 0;
	}
}