MoveableArrayList.java

/*
 * Copyright (c) 2008-2013, 2015, 2016 Eike Stepper (Berlin, Germany) and others.
 * 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:
 *    Eike Stepper - initial API and implementation
 */
package org.eclipse.net4j.util.collection;

import java.util.ArrayList;

/**
 * A list with O(1) effort for random access.
 * <p>
 * Whenever possible EMF's BasicEList should be used in favour of this list implementation.
 *
 * @author Eike Stepper
 */
public class MoveableArrayList<E> extends ArrayList<E> implements MoveableList<E>
{
  private static final long serialVersionUID = 1L;

  public MoveableArrayList(int initialCapacity)
  {
    super(initialCapacity);
  }

  /**
   * @since 3.0
   */
  public void move(int newPosition, Object object)
  {
    move(newPosition, indexOf(object));
  }

  public E move(int targetIndex, int sourceIndex)
  {
    int size = size();
    if (sourceIndex >= size)
    {
      throw new IndexOutOfBoundsException("sourceIndex=" + sourceIndex + ", size=" + size); //$NON-NLS-1$ //$NON-NLS-2$
    }

    if (targetIndex >= size)
    {
      throw new IndexOutOfBoundsException("targetIndex=" + targetIndex + ", size=" + size); //$NON-NLS-1$ //$NON-NLS-2$
    }

    E object = get(sourceIndex);
    if (targetIndex == sourceIndex)
    {
      return object;
    }

    if (targetIndex < sourceIndex)
    {
      moveUp1(targetIndex, sourceIndex - targetIndex);
    }
    else
    {
      moveDown1(targetIndex, targetIndex - sourceIndex);
    }

    set(targetIndex, object);
    return object;
  }

  private void moveUp1(int index, int count)
  {
    for (int i = count; i > 0; i--)
    {
      set(index + i, get(index + i - 1));
    }
  }

  private void moveDown1(int index, int count)
  {
    for (int i = count; i > 0; i--)
    {
      set(index - i, get(index - i + 1));
    }
  }
}