"unchecked or unsafe operations" compile error

[TheVader]

This error is driving me nuts. I've just got back to using Java again, after half a year or so, and now I can't seem to compile this very simple project.

I cannot add items (strings) to an ArrayList. I get the compile error ''Staafdiagram.java uses unchecked or unsafe operations.".

Can anyone help me with this?

import java.awt.*;
import java.applet.*;
import java.awt.event.*;
import java.util.*;

public class Staafdiagram extends Applet {

	public void paint(Graphics g) {
		ArrayList uni;
	        uni = new ArrayList();
        	uni.add("abc");
	}
}