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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 java.util.Iterator;
/**
* An {@code ImmutableSet} whose elements are derived by transforming another collection's elements,
* useful for {@code ImmutableMap.keySet()}.
*
* @author Jesse Wilson
*/
@GwtCompatible(emulated = true)
abstract class TransformedImmutableSet<D, E> extends ImmutableSet<E> {
/*
* TODO(cpovirk): using an abstract source() method instead of a field could simplify
* ImmutableMapKeySet, which currently has to pass in entrySet() manually
*/
final ImmutableCollection<D> source;
final int hashCode;
TransformedImmutableSet(ImmutableCollection<D> source) {
this.source = source;
this.hashCode = Sets.hashCodeImpl(this);
}
TransformedImmutableSet(ImmutableCollection<D> source, int hashCode) {
this.source = source;
this.hashCode = hashCode;
}
abstract E transform(D element);
@Override
public int size() {
return source.size();
}
@Override public boolean isEmpty() {
return false;
}
@Override public UnmodifiableIterator<E> iterator() {
final Iterator<D> backingIterator = source.iterator();
return new UnmodifiableIterator<E>() {
@Override
public boolean hasNext() {
return backingIterator.hasNext();
}
@Override
public E next() {
return transform(backingIterator.next());
}
};
}
@Override public Object[] toArray() {
return toArray(new Object[size()]);
}
@Override public <T> T[] toArray(T[] array) {
return ObjectArrays.toArrayImpl(this, array);
}
@Override public final int hashCode() {
return hashCode;
}
@GwtIncompatible("unused")
@Override boolean isHashCodeFast() {
return true;
}
}
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