Randomize in JAVA

I have problem with generate randomize number in loop.

Random rand = new Random();
public MyPanel(){
    super();
    setLayout(new BorderLayout());

    for(int y = 0; y < 10; y++)
        for(int x = 0; x < 20; x++){
            int n = rand.nextInt(4); // it should be generate another n in each repeat of loop? 
            b[x][y] = new Baloon(x*25, y*25,n); // n means color of baloon, I need this to get balloons with randomize colors.
            add(b[x][y]);
        }
}

Sorry for my English, i don't know this language perfectly.