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/*******************************************************************************
* Copyright (c) 2009, 2017 Cloudsmith Inc. and others.
*
* This program and the accompanying materials
* are made available under the terms of the Eclipse Public License 2.0
* which accompanies this distribution, and is available at
* https://www.eclipse.org/legal/epl-2.0/
*
* SPDX-License-Identifier: EPL-2.0
*
* Contributors:
* Cloudsmith Inc. - initial API and implementation
*******************************************************************************/
package org.eclipse.equinox.internal.p2.metadata.expression;
import java.util.Iterator;
import java.util.NoSuchElementException;
/**
* An iterator filter using a boolean {@link #isMatch(Object)} method.
*/
public abstract class MatchIteratorFilter<T> implements Iterator<T> {
private static final Object NO_ELEMENT = new Object();
private final Iterator<? extends T> innerIterator;
private T nextObject = noElement();
public MatchIteratorFilter(Iterator<? extends T> iterator) {
this.innerIterator = iterator;
}
@Override
public boolean hasNext() {
return positionNext();
}
@Override
public T next() {
if (!positionNext())
throw new NoSuchElementException();
T nxt = nextObject;
nextObject = noElement();
return nxt;
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
protected Iterator<? extends T> getInnerIterator() {
return innerIterator;
}
protected abstract boolean isMatch(T val);
private boolean positionNext() {
if (nextObject != NO_ELEMENT)
return true;
while (innerIterator.hasNext()) {
T nxt = innerIterator.next();
if (isMatch(nxt)) {
nextObject = nxt;
return true;
}
}
return false;
}
@SuppressWarnings("unchecked")
private static <T> T noElement() {
return (T) NO_ELEMENT;
}
}
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