/* * Copyright (C) 2008 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 java.util.Map; import javax.annotation.Nullable; /** * Implementation of {@link ImmutableMap} with exactly one entry. * * @author Jesse Wilson * @author Kevin Bourrillion */ @GwtCompatible(serializable = true, emulated = true) @SuppressWarnings("serial") // uses writeReplace(), not default serialization final class SingletonImmutableMap extends ImmutableMap { final transient K singleKey; final transient V singleValue; private transient Entry entry; SingletonImmutableMap(K singleKey, V singleValue) { this.singleKey = singleKey; this.singleValue = singleValue; } SingletonImmutableMap(Entry entry) { this.entry = entry; this.singleKey = entry.getKey(); this.singleValue = entry.getValue(); } private Entry entry() { Entry e = entry; return (e == null) ? (entry = Maps.immutableEntry(singleKey, singleValue)) : e; } @Override public V get(@Nullable Object key) { return singleKey.equals(key) ? singleValue : null; } @Override public int size() { return 1; } @Override public boolean isEmpty() { return false; } @Override public boolean containsKey(@Nullable Object key) { return singleKey.equals(key); } @Override public boolean containsValue(@Nullable Object value) { return singleValue.equals(value); } @Override boolean isPartialView() { return false; } private transient ImmutableSet> entrySet; @Override public ImmutableSet> entrySet() { ImmutableSet> es = entrySet; return (es == null) ? (entrySet = ImmutableSet.of(entry())) : es; } private transient ImmutableSet keySet; @Override public ImmutableSet keySet() { ImmutableSet ks = keySet; return (ks == null) ? (keySet = ImmutableSet.of(singleKey)) : ks; } private transient ImmutableCollection values; @Override public ImmutableCollection values() { ImmutableCollection v = values; return (v == null) ? (values = new Values(singleValue)) : v; } @SuppressWarnings("serial") // uses writeReplace(), not default serialization private static class Values extends ImmutableCollection { final V singleValue; Values(V singleValue) { this.singleValue = singleValue; } @Override public boolean contains(Object object) { return singleValue.equals(object); } @Override public boolean isEmpty() { return false; } @Override public int size() { return 1; } @Override public UnmodifiableIterator iterator() { return Iterators.singletonIterator(singleValue); } @Override boolean isPartialView() { return true; } } @Override public boolean equals(@Nullable Object object) { if (object == this) { return true; } if (object instanceof Map) { Map that = (Map) object; if (that.size() != 1) { return false; } Entry entry = that.entrySet().iterator().next(); return singleKey.equals(entry.getKey()) && singleValue.equals(entry.getValue()); } return false; } @Override public int hashCode() { return singleKey.hashCode() ^ singleValue.hashCode(); } @Override public String toString() { return new StringBuilder() .append('{') .append(singleKey.toString()) .append('=') .append(singleValue.toString()) .append('}') .toString(); } }