TransformationListIterator.java

/*******************************************************************************
 * Copyright (c) 1998, 2015 Oracle and/or its affiliates. All rights reserved.
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
 * which accompanies this distribution.
 * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *     Oracle - initial API and implementation from Oracle TopLink
******************************************************************************/
package org.eclipse.persistence.tools.workbench.utility.iterators;

import java.util.ListIterator;

import org.eclipse.persistence.tools.workbench.utility.ClassTools;
import org.eclipse.persistence.tools.workbench.utility.Transformer;


/**
 * A <code>TransformationListIterator</code> wraps another <code>ListIterator</code>
 * and transforms it results for client consumption. To use, supply a
 * <code>Transformer</code> or subclass <code>TransformationIterator</code>
 * and override the <code>transform(Object)</code> method.
 *
 * The methods <code>set(Object)</code> and <code>add(Object)</code>
 * are left unsupported in this class.
 */
public class TransformationListIterator implements ListIterator {
    private ListIterator nestedIterator;
    private Transformer transformer;

    /**
     * Construct an iterator with the specified nested iterator
     * and a transformer that simply returns the object, unchanged.
     * Use this constructor if you want to override the
     * <code>transform(Object)</code> method instead of building
     * a <code>Transformer</code>.
     */
    public TransformationListIterator(ListIterator nestedIterator) {
        this(nestedIterator, Transformer.NULL_INSTANCE);
    }

    /**
     * Construct an iterator with the specified nested iterator
     * and transformer.
     */
    public TransformationListIterator(ListIterator nestedIterator, Transformer transformer) {
        super();
        this.nestedIterator = nestedIterator;
        this.transformer = transformer;
    }

    /**
     * @see java.util.ListIterator#hasNext()
     */
    public boolean hasNext() {
        // delegate to the nested iterator
        return this.nestedIterator.hasNext();
    }

    /**
     * @see java.util.ListIterator#next()
     */
    public Object next() {
        // transform the object returned by the nested iterator before returning it
        return this.transform(this.nestedIterator.next());
    }

    /**
     * @see java.util.ListIterator#nextIndex()
     */
    public int nextIndex() {
        // delegate to the nested iterator
        return this.nestedIterator.nextIndex();
    }

    /**
     * @see java.util.ListIterator#hasPrevious()
     */
    public boolean hasPrevious() {
        // delegate to the nested iterator
        return this.nestedIterator.hasPrevious();
    }

    /**
     * @see java.util.ListIterator#previous()
     */
    public Object previous() {
        // transform the object returned by the nested iterator before returning it
        return this.transform(this.nestedIterator.previous());
    }

    /**
     * @see java.util.ListIterator#previousIndex()
     */
    public int previousIndex() {
        // delegate to the nested iterator
        return this.nestedIterator.previousIndex();
    }

    /**
     * @see java.util.ListIterator#add(Object)
     */
    public void add(Object o) {
        throw new UnsupportedOperationException();
    }

    /**
     * @see java.util.ListIterator#set(Object)
     */
    public void set(Object o) {
        throw new UnsupportedOperationException();
    }

    /**
     * @see java.util.ListIterator#remove()
     */
    public void remove() {
        // delegate to the nested iterator
        this.nestedIterator.remove();
    }

    /**
     * Transform the specified object and return the result.
     */
    protected Object transform(Object next) {
        return this.transformer.transform(next);
    }

    /**
     * @see java.lang.Object#toString()
     */
    public String toString() {
        return ClassTools.shortClassNameForObject(this) + '(' + this.nestedIterator + ')';
    }
}