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/*
* Copyright (C) 2011 The Android Open Source Project
*
* 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 android.util;
import java.util.AbstractSet;
import java.util.Iterator;
/**
* A fast immutable set wrapper for an array that is optimized for non-concurrent iteration.
* The same iterator instance is reused each time to avoid creating lots of garbage.
* Iterating over an array in this fashion is 2.5x faster than iterating over a {@link HashSet}
* so it is worth copying the contents of the set to an array when iterating over it
* hundreds of times.
* @hide
*/
public final class FastImmutableArraySet<T> extends AbstractSet<T> {
FastIterator<T> mIterator;
T[] mContents;
public FastImmutableArraySet(T[] contents) {
mContents = contents;
}
@Override
public Iterator<T> iterator() {
FastIterator<T> it = mIterator;
if (it == null) {
it = new FastIterator<T>(mContents);
mIterator = it;
} else {
it.mIndex = 0;
}
return it;
}
@Override
public int size() {
return mContents.length;
}
private static final class FastIterator<T> implements Iterator<T> {
private final T[] mContents;
int mIndex;
public FastIterator(T[] contents) {
mContents = contents;
}
@Override
public boolean hasNext() {
return mIndex != mContents.length;
}
@Override
public T next() {
return mContents[mIndex++];
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
}
}
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