Your own auto-growth Array : Auto Grow Array « Collections « Java Tutorial

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2. Collections
3. Auto Grow Array

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 * 
 * The Apache Software License, Version 1.1
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 * reserved.
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 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer. 
 *
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 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowlegement:  
 *       "This product includes software developed by the 
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
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 * 4. The names "The Jakarta Project", "Jakarta Element Construction Set", 
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public class Array implements java.util.Enumeration,java.io.Serializable
{
    private int current = 0;
    private int size = 10;
    private int grow = 2;
    private int place = 0;
    private Object[] elements = null;
    private Object[] tmpElements = null;

    public Array()
    {
        init();
    }

    public Array(int size)
    {
        setSize(size);
        init();
    }

    public Array(int size,int grow)
    {
        setSize(size);
        setGrow(grow);
        init();
    }

    private void init()
    {
        elements = new Object[size];
    }

    public Object nextElement() throws java.util.NoSuchElementException
    {
        if ( elements[place] != null && place != current)
        {
            place++;
            return elements[place - 1];
        }
        else
        {
            place = 0;
            throw new java.util.NoSuchElementException();
        }
    }

    public boolean hasMoreElements()
    {
        if( place < elements.length && current != place )
            return true;
        return false;
    }

    public void setSize(int size)
    {
        this.size = size;
    }

    public int getCurrentSize()
    {
        return current;
    }

    public void rehash()
    {
        tmpElements = new Object[size];
        int count = 0;
        for ( int x = 0; x < elements.length; x++ )
        {
            if( elements[x] != null )
            {
                tmpElements[count] = elements[x];
                count++;
            }
        }
        elements = (Object[])tmpElements.clone();
        tmpElements = null;
        current = count;
    }

    public void setGrow(int grow)
    {
        this.grow = grow;
    }

    public void grow()
    {
        size = size+=(size/grow);
        rehash();
    }

    public void add(Object o)
    {
        if( current == elements.length )
            grow();

        try
        {
            elements[current] = o;
            current++;
        }
        catch(java.lang.ArrayStoreException ase)
        {
        }
    }

    public void add(int location,Object o)
    {
        try
        {
            elements[location] = o;
        }
        catch(java.lang.ArrayStoreException ase)
        {
        }
    }

    public void remove(int location)
    {
        elements[location] = null;
    }

    public int location(Object o) throws NoSuchObjectException
    {
        int loc = -1;
        for ( int x = 0; x < elements.length; x++ )
        {
            if((elements[x] != null && elements[x] == o )||
               (elements[x] != null && elements[x].equals(o)))
            {
                loc = x;
                break;
            }
        }
        if( loc == -1 )
            throw new NoSuchObjectException();
        return(loc);
    }

    public Object get(int location)
    {
        return elements[location];
    }

    public java.util.Enumeration elements()
    {
        return this;
    }
}
class NoSuchObjectException extends Exception
{

    public NoSuchObjectException()
    {
        super("No such object found.");
    }
}