What will be the output of the following Java program?

interface calculate
{
    void cal(int item);
}
class display implements calculate
{
    int x;
    public void cal(int item)
    {
        x = item * item;            
    }
}
class interfaces
{
    public static void main(String args[])
    {
        display arr = new display;
        arr.x = 0;      
        arr.cal(2);
        System.out.print(arr.x);
    }
}