/**
 * @author MUHAMMAD AZRI BIN JASNI @ ABDUL RANI
 * @version 27 SEPTEMBER 2012
 */
public class ArrayList
{
    // instance variables
    public int length;
    public int maxSize;// maxSize default at 100
    public Object [] list;

    /**
     * Constructor for objects of class ArrayList
     */
    public ArrayList(){
         this.length = 0;
         maxSize=100;
         list = new Object[maxSize];
         for (int i=0;i<maxSize;i++)
            list[i] = new Object();
    }

    public ArrayList(int size)
    {
        this.length = 0;
        maxSize=size;
        list= new Object[maxSize];
        for (int i=0;i<maxSize;i++)
           list[i] = new Object();
    }

    /**methods**/
    public boolean isEmpty()
    {
        return (length==0);
    }

    public boolean isFull()
    {
        return (length==maxSize);
    }

    public void insertAtFront(Object a)
    {
        if (isFull())
        {
            System.err.println("Can't insert in full list.");
        }
        else
        {
            if (! isEmpty())
            {
                for(int i = length; i > 0; i--)
                    list[i] = list[i - 1];
            }
            //if (isEmpty())
            //    list = new Object[1];
            list [0] = a;
            length++;
        }
    }//end insertAtFront

    public void insertAtBack(Object a)
    {
    if (isFull())
        {
            System.err.println("Can't insert in full list.");
        }
        else
        {
            list [length] = a;
            length++;
        }
     }//end insertAtBack

    public void insertAt(Object a, int index)//replace element[index] with item
    {
        if (isFull())
            System.err.println("Can't insert in full list.");
        else
            list[index]=a;
    }

     public void removeFromFront()
     {
        if (isEmpty())
        {
            System.err.println("Can't remove in empty list.");
        }
        else
        {
            for(int i = 0; i <length; i++)
                list[i] = list[i+1];
            length--;
        }
    }

    public void removeFromBack()
    {
    if (isEmpty())
        {
            System.err.println("Can't remove in empty list.");
        }
        else
        {
            list[length] = null;
            length--;
        }
    }

    public void display()
    {
        for(int i = 0; i <length; i++)
        {
            System.out.print(list[i]+" ");
        }
        System.out.println("");
    }
}