1/* 2 * Copyright (C) 2008 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 17package com.google.common.collect; 18 19import com.google.common.annotations.GwtCompatible; 20import com.google.common.annotations.GwtIncompatible; 21 22import java.util.Collection; 23import java.util.Comparator; 24import java.util.NoSuchElementException; 25import java.util.Set; 26 27import javax.annotation.Nullable; 28 29/** 30 * An empty immutable sorted set. 31 * 32 * @author Jared Levy 33 */ 34@GwtCompatible(serializable = true, emulated = true) 35@SuppressWarnings("serial") // uses writeReplace(), not default serialization 36class EmptyImmutableSortedSet<E> extends ImmutableSortedSet<E> { 37 EmptyImmutableSortedSet(Comparator<? super E> comparator) { 38 super(comparator); 39 } 40 41 @Override 42 public int size() { 43 return 0; 44 } 45 46 @Override public boolean isEmpty() { 47 return true; 48 } 49 50 @Override public boolean contains(@Nullable Object target) { 51 return false; 52 } 53 54 @Override public boolean containsAll(Collection<?> targets) { 55 return targets.isEmpty(); 56 } 57 58 @Override public UnmodifiableIterator<E> iterator() { 59 return Iterators.emptyIterator(); 60 } 61 62 @GwtIncompatible("NavigableSet") 63 @Override public UnmodifiableIterator<E> descendingIterator() { 64 return Iterators.emptyIterator(); 65 } 66 67 @Override boolean isPartialView() { 68 return false; 69 } 70 71 @Override public ImmutableList<E> asList() { 72 return ImmutableList.of(); 73 } 74 75 @Override 76 int copyIntoArray(Object[] dst, int offset) { 77 return offset; 78 } 79 80 @Override public boolean equals(@Nullable Object object) { 81 if (object instanceof Set) { 82 Set<?> that = (Set<?>) object; 83 return that.isEmpty(); 84 } 85 return false; 86 } 87 88 @Override public int hashCode() { 89 return 0; 90 } 91 92 @Override public String toString() { 93 return "[]"; 94 } 95 96 @Override 97 public E first() { 98 throw new NoSuchElementException(); 99 } 100 101 @Override 102 public E last() { 103 throw new NoSuchElementException(); 104 } 105 106 @Override 107 ImmutableSortedSet<E> headSetImpl(E toElement, boolean inclusive) { 108 return this; 109 } 110 111 @Override 112 ImmutableSortedSet<E> subSetImpl( 113 E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) { 114 return this; 115 } 116 117 @Override 118 ImmutableSortedSet<E> tailSetImpl(E fromElement, boolean inclusive) { 119 return this; 120 } 121 122 @Override int indexOf(@Nullable Object target) { 123 return -1; 124 } 125 126 @Override 127 ImmutableSortedSet<E> createDescendingSet() { 128 return new EmptyImmutableSortedSet<E>(Ordering.from(comparator).reverse()); 129 } 130} 131