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/*
* Copyright (C) 2007 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 com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.J2ktIncompatible;
import com.google.common.base.Preconditions;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;
/**
* Implementation of {@link ImmutableSet} with exactly one element.
*
* @author Kevin Bourrillion
* @author Nick Kralevich
*/
@GwtCompatible(serializable = true, emulated = true)
@SuppressWarnings("serial") // uses writeReplace(), not default serialization
@ElementTypesAreNonnullByDefault
final class SingletonImmutableSet<E> extends ImmutableSet<E> {
// We deliberately avoid caching the asList and hashCode here, to ensure that with
// compressed oops, a SingletonImmutableSet packs all the way down to the optimal 16 bytes.
final transient E element;
SingletonImmutableSet(E element) {
this.element = Preconditions.checkNotNull(element);
}
@Override
public int size() {
return 1;
}
@Override
public boolean contains(@CheckForNull Object target) {
return element.equals(target);
}
@Override
public UnmodifiableIterator<E> iterator() {
return Iterators.singletonIterator(element);
}
@Override
public ImmutableList<E> asList() {
return ImmutableList.of(element);
}
@Override
boolean isPartialView() {
return false;
}
@Override
int copyIntoArray(@Nullable Object[] dst, int offset) {
dst[offset] = element;
return offset + 1;
}
@Override
public final int hashCode() {
return element.hashCode();
}
@Override
public String toString() {
return '[' + element.toString() + ']';
}
// redeclare to help optimizers with b/310253115
@SuppressWarnings("RedundantOverride")
@Override
@J2ktIncompatible // serialization
@GwtIncompatible // serialization
Object writeReplace() {
return super.writeReplace();
}
}
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