Array-List for integer objects. : Auto Grow Array « Collections « Java Tutorial

1. Java Tutorial
2. Collections
3. Auto Grow Array

/**
 * 
 * JFreeReport : a free Java reporting library
 * 
 *
 * Project Info:  http://reporting.pentaho.org/
 *
 * (C) Copyright 2001-2007, by Object Refinery Ltd, Pentaho Corporation and Contributors.
 *
 * This library is free software; you can redistribute it and/or modify it under the terms
 * of the GNU Lesser General Public License as published by the Free Software Foundation;
 * either version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License along with this
 * library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
 * Boston, MA 02111-1307, USA.
 *
 * [Java is a trademark or registered trademark of Sun Microsystems, Inc.
 * in the United States and other countries.]
 *
 * ------------
 * LongList.java
 * ------------
 * (C) Copyright 2001-2007, by Object Refinery Ltd, Pentaho Corporation and Contributors.
 */

import java.io.Serializable;

/**
 * A Array-List for integer objects. Ints can be added to the list and will be stored in an int-array.
 * <p/>
 * Using this list for storing ints is much faster than creating java.lang.Long objects and storing them in an
 * ArrayList.
 * <p/>
 * This list is not synchronized and does not implement the full List interface. In fact, this list can only be used to
 * add new values or to clear the complete list.
 *
 * @author Thomas Morgner
 */
public class LongList implements Serializable, Cloneable
{
  /**
   * An empty array used to avoid object creation.
   */
  private static final long[] EMPTY_ARRAY = new long[0];
  /**
   * The array holding the list data.
   */
  private long[] data;
  /**
   * The size of the list.
   */
  private int size;
  /**
   * The number of free slots added on every resize.
   */
  private int increment;

  /**
   * Creates a new IntList with the given initial capacity. The capacity will also be used as increment value when
   * extending the capacity of the list.
   *
   * @param capacity the initial capacity.
   */
  public LongList(final int capacity)
  {
    data = new long[capacity];
    increment = capacity;
  }

  /**
   * Ensures, that the list backend can store at least <code>c</code> elements. This method does nothing, if the new
   * capacity is less than the current capacity.
   *
   * @param c the new capacity of the list.
   */
  private void ensureCapacity(final int c)
  {
    if (data.length <= c)
    {
      final long[] newData = new long[Math.max(data.length + increment, c + 1)];
      System.arraycopy(data, 0, newData, 0, size);
      data = newData;
    }
  }

  /**
   * Adds the given int value to the list.
   *
   * @param value the new value to be added.
   */
  public void add(final long value)
  {
    ensureCapacity(size);
    data[size] = value;
    size += 1;
  }

  /**
   * Adds the given int value to the list.
   *
   * @param value the new value to be defined.
   * @param index the position of the valur that should be redefined.
   */
  public void set(final int index, final long value)
  {
    ensureCapacity(index);
    data[index] = value;
    if (index >= size)
    {
      size = index + 1;
    }
  }


  /**
   * Returns the value at the given index.
   *
   * @param index the index
   * @return the value at the given index
   * @throws IndexOutOfBoundsException if the index is greater or equal to the list size or if the index is negative.
   */
  public long get(final int index)
  {
    if (index >= size || index < 0)
    {
      throw new IndexOutOfBoundsException("Illegal Index: " + index + " Max:" + size);
    }
    return data[index];
  }

  /**
   * Clears the list.
   */
  public void clear()
  {
    size = 0;
  }

  /**
   * Returns the number of elements in this list.
   *
   * @return the number of elements in the list
   */
  public int size()
  {
    return size;
  }

  /**
   * Copys the list contents into a new array.
   *
   * @return the list contents as array.
   */
  public long[] toArray()
  {
    if (size == 0)
    {
      return LongList.EMPTY_ARRAY;
    }

    if (size == data.length)
    {
      return (long[]) data.clone();
    }

    final long[] retval = new long[size];
    System.arraycopy(data, 0, retval, 0, size);
    return retval;
  }

  /**
   * Copys the list contents into a new array.
   *
   * @param retval the array that should receive the contents.
   * @return the list contents as array.
   */
  public long[] toArray(long[] retval)
  {
    if (retval == null || retval.length < size)
    {
      retval =  new long[size];
    }
    System.arraycopy(data, 0, retval, 0, size);
    return retval;
  }

  /**
   * Creates a copy of this list.
   *
   * @return a copy of this list.
   * @throws CloneNotSupportedException if something went wrong during the cloning.
   */
  public Object clone() throws CloneNotSupportedException
  {
    final LongList intList = (LongList) super.clone();
    intList.data = (long[]) data.clone();
    return data;
  }
}