Why is my rectangle showing up in a strange form in my JPanel?

Question

When I run my code, a rectangle shows up only when the mouse is clicked in the top left corner of the JPanel. When it shows up, it is warped out of shape. If I change fillRect to fillOval, it does not show up at all. My goal is to have a circle filled at the mouse's location when it is clicked. My code is:

import java.awt.event.*;
import java.awt.*;
import javax.swing.*;
public class PaintProgram {
    JFrame frame;
    JPanel panel;
    Point p;
    int x;
    int y;
    int diameter;
    public PaintProgram(){
        frame = new JFrame();
        frame.setSize(500,500);
        panel = new JPanel();
        diameter = 100;
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        panel.addMouseListener(new MListener());
        panel.add(new DrawCircle());
        frame.add(panel);
        frame.setVisible(true);
    }

    public static void main(String[] args){
        PaintProgram p = new PaintProgram();
    }

    class UBListener implements ActionListener{
        @Override
        public void actionPerformed(ActionEvent a){

        }
    }


    class MListener implements MouseListener{
        public void mousePressed(MouseEvent e){
            p = panel.getMousePosition();
            x = (int) p.getX();
            y = (int) p.getY();
            panel.add(new DrawCircle());
            frame.repaint();
            frame.revalidate();
            System.out.println(x + "," + y);
        }

        public void mouseReleased(MouseEvent e){
        }

        public void mouseClicked(MouseEvent e){
        }

        public void mouseExited(MouseEvent e){
        }

        public void mouseEntered(MouseEvent e){
        }
    }

    class DrawCircle extends JPanel{
        @Override
        public void paintComponent(Graphics g){
            super.paintComponent(g);
            g.setColor(Color.orange);
            g.fillRect(x,y,diameter,diameter);
            System.out.println(x + "," + y);
        }
    }
}

Answer 1

I think there were a couple issues with your code. First, your JPanel defined in PaintProgram is not necessary and was causing some issues in your code. Basically I have switched to using the JFrame for just about everything. Next, I don't think you want to create a new DrawCircle() in PaintProgram, just on mouse click.

The following code works for me (draws a circle around your cursor whenever you click, which I think is what you wanted). I made a few changes I didn't mention so feel free to ask questions.

import java.awt.event.*;
import java.awt.*;
import javax.swing.*;

public class PaintProgram {
    JFrame frame;
    Point p;
    int x;
    int y;
    int diameter;
    public PaintProgram(){
        frame = new JFrame();
        frame.setSize(500,500);
        diameter = 100;
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.addMouseListener(new MListener());
        frame.setVisible(true);
    }

    public static void main(String[] args){
        PaintProgram p = new PaintProgram();
    }

    class UBListener implements ActionListener{
        @Override
        public void actionPerformed(ActionEvent a){

        }
    }


    class MListener extends MouseAdapter {
       @Override
       public void mousePressed(MouseEvent e){
            p = frame.getMousePosition();
            x = (int) p.getX();
            y = (int) p.getY();
            frame.add(new DrawCircle());
            frame.repaint();
            frame.revalidate();
            System.out.println(x + "," + y);
        }
    }

    class DrawCircle extends JPanel{
        @Override
        public void paintComponent(Graphics g){
            g.setColor(Color.orange);
            g.fillOval(x - 56, y - 77, diameter, diameter);
            System.out.println(x + "," + y);
        }
    }
}