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/*******************************************************************************
* Copyright (c) 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.utility.internal.iterables;
import java.util.Iterator;
import org.eclipse.jpt.utility.internal.StringTools;
import org.eclipse.jpt.utility.internal.Transformer;
import org.eclipse.jpt.utility.internal.iterators.TransformationIterator;
/**
* A <code>TransformationIterable</code> wraps another {@link Iterable}
* and transforms its elements for client consumption. To use, supply a
* {@link Transformer} or subclass <code>TransformationIterable</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 iterable's 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 iterable's iterator
*
* @see TransformationIterator
* @see TransformationListIterable
*/
public class TransformationIterable<E1, E2>
implements Iterable<E2>
{
private final Iterable<? extends E1> iterable;
private final Transformer<E1, ? extends E2> transformer;
/**
* Construct an iterable with the specified nested iterable
* and a default transformer that calls back to the iterable.
* Use this constructor if you want to override the
* {@link #transform(Object)} method instead of building
* a {@link Transformer}.
*/
public TransformationIterable(Iterable<? extends E1> iterable) {
super();
this.iterable = iterable;
this.transformer = this.buildDefaultTransformer();
}
/**
* Construct an iterable with the specified nested iterable
* and transformer.
*/
public TransformationIterable(Iterable<? extends E1> iterable, Transformer<E1, ? extends E2> transformer) {
super();
this.iterable = iterable;
this.transformer = transformer;
}
protected Transformer<E1, ? extends E2> buildDefaultTransformer() {
return new DefaultTransformer();
}
public Iterator<E2> iterator() {
return new TransformationIterator<E1, E2>(this.iterable.iterator(), this.transformer);
}
/**
* Transform the specified object and return the result.
*/
protected E2 transform(@SuppressWarnings("unused") E1 o) {
throw new RuntimeException("This method was not overridden."); //$NON-NLS-1$
}
@Override
public String toString() {
return StringTools.buildToStringFor(this, this.iterable);
}
//********** default linker **********
protected class DefaultTransformer implements Transformer<E1, E2> {
public E2 transform(E1 o) {
return TransformationIterable.this.transform(o);
}
}
}
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