1 /* 2 * Copyright (C) 2009 The Guava Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.google.common.collect; 18 19 import com.google.common.annotations.GwtCompatible; 20 21 import java.io.Serializable; 22 import java.util.Collection; 23 import java.util.EnumSet; 24 25 /** 26 * Implementation of {@link ImmutableSet} backed by a non-empty {@link 27 * java.util.EnumSet}. 28 * 29 * @author Jared Levy 30 */ 31 @GwtCompatible(serializable = true, emulated = true) 32 @SuppressWarnings("serial") // we're overriding default serialization 33 final class ImmutableEnumSet<E extends Enum<E>> extends ImmutableSet<E> { 34 static <E extends Enum<E>> ImmutableSet<E> asImmutable(EnumSet<E> set) { 35 switch (set.size()) { 36 case 0: 37 return ImmutableSet.of(); 38 case 1: 39 return ImmutableSet.of(Iterables.getOnlyElement(set)); 40 default: 41 return new ImmutableEnumSet<E>(set); 42 } 43 } 44 45 /* 46 * Notes on EnumSet and <E extends Enum<E>>: 47 * 48 * This class isn't an arbitrary ForwardingImmutableSet because we need to 49 * know that calling {@code clone()} during deserialization will return an 50 * object that no one else has a reference to, allowing us to guarantee 51 * immutability. Hence, we support only {@link EnumSet}. 52 */ 53 private final transient EnumSet<E> delegate; 54 55 private ImmutableEnumSet(EnumSet<E> delegate) { 56 this.delegate = delegate; 57 } 58 59 @Override boolean isPartialView() { 60 return false; 61 } 62 63 @Override public UnmodifiableIterator<E> iterator() { 64 return Iterators.unmodifiableIterator(delegate.iterator()); 65 } 66 67 @Override 68 public int size() { 69 return delegate.size(); 70 } 71 72 @Override public boolean contains(Object object) { 73 return delegate.contains(object); 74 } 75 76 @Override public boolean containsAll(Collection<?> collection) { 77 return delegate.containsAll(collection); 78 } 79 80 @Override public boolean isEmpty() { 81 return delegate.isEmpty(); 82 } 83 84 @Override public boolean equals(Object object) { 85 return object == this || delegate.equals(object); 86 } 87 88 private transient int hashCode; 89 90 @Override public int hashCode() { 91 int result = hashCode; 92 return (result == 0) ? hashCode = delegate.hashCode() : result; 93 } 94 95 @Override public String toString() { 96 return delegate.toString(); 97 } 98 99 // All callers of the constructor are restricted to <E extends Enum<E>>. 100 @Override Object writeReplace() { 101 return new EnumSerializedForm<E>(delegate); 102 } 103 104 /* 105 * This class is used to serialize ImmutableEnumSet instances. 106 */ 107 private static class EnumSerializedForm<E extends Enum<E>> 108 implements Serializable { 109 final EnumSet<E> delegate; 110 EnumSerializedForm(EnumSet<E> delegate) { 111 this.delegate = delegate; 112 } 113 Object readResolve() { 114 // EJ2 #76: Write readObject() methods defensively. 115 return new ImmutableEnumSet<E>(delegate.clone()); 116 } 117 private static final long serialVersionUID = 0; 118 } 119 } 120
