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The local variable g may not have been initialized

The local variable g may not have been initialized

The local variable g may not have been initialized

(OP)
Hi,

I try to drawOval in the JFrame as below (I want it as simple as possible). However, it not works. Can you tell me what I am missing?

import javax.swing.*;
import java.awt.*;
public class MyFrameClass {
    public static void main(String[] args) {
        JFrame frame = new JFrame();
        frame.setSize(500,300);
        frame.setVisible(true);
        Graphics g;
        g.drawOval(100,100,400,200);  //error: The local variable g may not have been initialized.
    }
}

RE: The local variable g may not have been initialized

You have indeed defined the variable g as being a Graphic, but not filled it with an instance (using 'new') before you try to draw the oval at it.  

RE: The local variable g may not have been initialized

(OP)
Thank TonHu.

Perhaps, I need to tell Java that I need to draw on the frame, but I don't know how.

I have just tried
Graphics g = new Graphics();
but got error: Cannot instantiate the type Graphics

RE: The local variable g may not have been initialized

You have to override the paint methof JFrame like here

Cheers,
Dian

RE: The local variable g may not have been initialized

(OP)
Thanks Dian, I am reading your link which must be usefull!

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