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/*******************************************************************************
* Copyright (c) 2005, 2009 Oracle. All rights reserved.
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0, which accompanies this distribution
* and is available at http://www.eclipse.org/legal/epl-v10.html.
*
* Contributors:
* Oracle - initial API and implementation
******************************************************************************/
package org.eclipse.jpt.common.utility.internal.iterators;
import java.util.Iterator;
import org.eclipse.jpt.common.utility.internal.StringTools;
import org.eclipse.jpt.common.utility.internal.Transformer;
/**
* A <code>TransformationIterator</code> wraps another {@link Iterator}
* and transforms its results for client consumption. To use, supply a
* {@link Transformer} or subclass <code>TransformationIterator</code>
* and override the {@link #transform(Object)} method.
* Objects of type <code>E1</code> are transformed into objects of type <code>E2</code>;
* i.e. the iterator returns objects of type <code>E2</code>.
*
* @param <E1> input: the type of elements to be transformed
* @param <E2> output: the type of elements returned by the iterator
*
* @see org.eclipse.jpt.common.utility.internal.iterables.TransformationIterable
*/
public class TransformationIterator<E1, E2>
implements Iterator<E2>
{
private final Iterator<? extends E1> iterator;
private final Transformer<E1, ? extends E2> transformer;
/**
* Construct an iterator with the specified iterable
* and a disabled transformer.
* Use this constructor if you want to override the
* {@link #transform(Object)} method instead of building
* a {@link Transformer}.
*/
public TransformationIterator(Iterable<? extends E1> iterable) {
this(iterable.iterator());
}
/**
* Construct an iterator with the specified nested iterator
* and a disabled transformer.
* Use this constructor if you want to override the
* {@link #transform(Object)} method instead of building
* a {@link Transformer}.
*/
public TransformationIterator(Iterator<? extends E1> iterator) {
this(iterator, Transformer.Disabled.<E1, E2>instance());
}
/**
* Construct an iterator with the specified iterable and transformer.
*/
public TransformationIterator(Iterable<? extends E1> iterable, Transformer<E1, ? extends E2> transformer) {
this(iterable.iterator(), transformer);
}
/**
* Construct an iterator with the specified nested iterator
* and transformer.
*/
public TransformationIterator(Iterator<? extends E1> iterator, Transformer<E1, ? extends E2> transformer) {
super();
this.iterator = iterator;
this.transformer = transformer;
}
public boolean hasNext() {
// delegate to the nested iterator
return this.iterator.hasNext();
}
public E2 next() {
// transform the object returned by the nested iterator before returning it
return this.transform(this.iterator.next());
}
public void remove() {
// delegate to the nested iterator
this.iterator.remove();
}
/**
* Transform the specified object and return the result.
*/
protected E2 transform(E1 next) {
return this.transformer.transform(next);
}
@Override
public String toString() {
return StringTools.buildToStringFor(this, this.iterator);
}
}
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