Question

import java.awt.*; 

import java.awt.event.*;

import javax.swing.*;

public class Stickman extends JPanel{

    public void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        //Color SKY = new Color(135, 206, 235);
        this.setBackground(Color.WHITE);

        g.setColor(Color.BLUE);
        g.fillRect(30, 100, 10, 5);

        g.setColor(Color.gray);
        g.fillRect(30, 120, 10, 5);

    }
}

---

import javax.swing.*;

public class WindowPerameters {

    public static void main (String[] args)
    {
        JFrame f = new JFrame ("Hangman");

        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        Stickman s = new Stickman();

        f.add(s);

        f.setSize(600, 300);

        f.setVisible(true);

    }

}

Answer 1

You’re not executing the Swing code inside the event dispatch thread. See http://docs.oracle.com/javase/6/docs/api/javax/swing/package-summary.html#threading.

Also, you shouldn’t change the panel’s background inside the paintComponent method. Use this method to paint the component, but not to modify its properties.