"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");
	}
}

[System_Error]

This compiled fine for me. You might be using an older version of java or something.

[CornedBee]

Actually, I think he's using a very new version. Some Java 5 compilers I've seen emit this warning (a warning, mind you, the compiling still works) if you're not using generics when you can, which is generally less safe than using them. ArrayList being the case. Make it an ArrayList<String> and it should compile fine.

If your code is really Java 1.4, pass the "-source 1.4" switch to the compiler. This will eliminate the warning/error as well.

[TheVader]

Thanks, that was it indeed. I was using Java 1.5. I downgraded to version 1.4.2. Perhaps later on I'll reinstall 1.5 and see what advantages it brings; but for now I have a deadline to overcome.