108 lines
2.1 KiB
Java
108 lines
2.1 KiB
Java
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/*
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* Copyright (C) 2007 The Guava Authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.common.collect;
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import java.util.Collection;
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import java.util.Set;
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import javax.annotation.Nullable;
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import com.google.common.annotations.GwtCompatible;
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/**
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* An empty immutable set.
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*
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* @author Kevin Bourrillion
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*/
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@GwtCompatible(serializable = true, emulated = true)
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final class EmptyImmutableSet extends ImmutableSet<Object> {
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static final EmptyImmutableSet INSTANCE = new EmptyImmutableSet();
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private EmptyImmutableSet() {
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}
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@Override
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public int size() {
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return 0;
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}
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@Override
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public boolean isEmpty() {
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return true;
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}
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@Override
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public boolean contains(@Nullable Object target) {
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return false;
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}
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@Override
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public boolean containsAll(Collection<?> targets) {
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return targets.isEmpty();
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}
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@Override
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public UnmodifiableIterator<Object> iterator() {
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return Iterators.emptyIterator();
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}
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@Override
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boolean isPartialView() {
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return false;
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}
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@Override
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int copyIntoArray(Object[] dst, int offset) {
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return offset;
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}
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@Override
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public ImmutableList<Object> asList() {
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return ImmutableList.of();
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}
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@Override
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public boolean equals(@Nullable Object object) {
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if (object instanceof Set) {
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Set<?> that = (Set<?>) object;
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return that.isEmpty();
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}
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return false;
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}
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@Override
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public final int hashCode() {
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return 0;
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}
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@Override
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boolean isHashCodeFast() {
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return true;
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}
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@Override
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public String toString() {
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return "[]";
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}
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Object readResolve() {
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return INSTANCE; // preserve singleton property
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}
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private static final long serialVersionUID = 0;
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}
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