[hardwired]

Code:

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

public class PaintHere extends JPanel {
    int x = -30;
    int y = -30;

    public PaintHere() {
        addMouseListener(clicker);
    }

    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALIAS_ON);
        g2.drawRect(x, y, 30, 30);
    }

    private MouseListener clicker = new MouseAdapter() {
        public void mousePressed(MouseEvent e) {
            x = e.getX();
            y = e.getY();
            repaint();
        }
    };

    public static void main(String[] args) {
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(new PaintHere());
        f.setSize(300,300);
        f.setLocation(200,200);
        f.setVisible(true);
    }
}