1 /* 2 * Copyright (C) 2009 Google Inc. 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 import java.util.Set; 25 26 /** 27 * Implementation of {@link ImmutableSet} backed by a non-empty {@link 28 * java.util.EnumSet}. 29 * 30 * @author Jared Levy 31 */ 32 @GwtCompatible(serializable = true) 33 @SuppressWarnings("serial") // we're overriding default serialization 34 final class ImmutableEnumSet<E /*extends Enum<E>*/> extends ImmutableSet<E> { 35 /* 36 * Notes on EnumSet and <E extends Enum<E>>: 37 * 38 * This class isn't an arbitrary ForwardingImmutableSet because we need to 39 * know that calling {@code clone()} during deserialization will return an 40 * object that no one else has a reference to, allowing us to guarantee 41 * immutability. Hence, we support only {@link EnumSet}. 42 * 43 * GWT complicates matters. If we declare the class's type parameter as 44 * <E extends Enum<E>> (as is necessary to declare a field of type 45 * EnumSet<E>), GWT generates serializers for every available enum. This 46 * increases the size of some applications' JavaScript by over 10%. To avoid 47 * this, we declare the type parameter as just <E> and the field as just 48 * Set<E>. writeReplace() must then use an unchecked cast to return to 49 * EnumSet, guaranteeing immutability as described above. 50 */ 51 private final transient Set<E> delegate; 52 53 ImmutableEnumSet(Set<E> delegate) { 54 this.delegate = delegate; 55 } 56 57 @Override public UnmodifiableIterator<E> iterator() { 58 return Iterators.unmodifiableIterator(delegate.iterator()); 59 } 60 61 public int size() { 62 return delegate.size(); 63 } 64 65 @Override public boolean contains(Object object) { 66 return delegate.contains(object); 67 } 68 69 @Override public boolean containsAll(Collection<?> collection) { 70 return delegate.containsAll(collection); 71 } 72 73 @Override public boolean isEmpty() { 74 return delegate.isEmpty(); 75 } 76 77 @Override public Object[] toArray() { 78 return delegate.toArray(); 79 } 80 81 @Override public <T> T[] toArray(T[] array) { 82 return delegate.toArray(array); 83 } 84 85 @Override public boolean equals(Object object) { 86 return object == this || delegate.equals(object); 87 } 88 89 private transient int hashCode; 90 91 @Override public int hashCode() { 92 int result = hashCode; 93 return (result == 0) ? hashCode = delegate.hashCode() : result; 94 } 95 96 @Override public String toString() { 97 return delegate.toString(); 98 } 99 100 // All callers of the constructor are restricted to <E extends Enum<E>>. 101 @SuppressWarnings("unchecked") 102 @Override Object writeReplace() { 103 return new EnumSerializedForm((EnumSet) delegate); 104 } 105 106 /* 107 * This class is used to serialize ImmutableEnumSet instances. 108 */ 109 private static class EnumSerializedForm<E extends Enum<E>> 110 implements Serializable { 111 final EnumSet<E> delegate; 112 EnumSerializedForm(EnumSet<E> delegate) { 113 this.delegate = delegate; 114 } 115 Object readResolve() { 116 // EJ2 #76: Write readObject() methods defensively. 117 return new ImmutableEnumSet<E>(delegate.clone()); 118 } 119 private static final long serialVersionUID = 0; 120 } 121 } 122
