Two threads doesn't work simultaneously

[przenica]

I've created class Zegary that extends JPanel and implements Runnable. Then I've created two objects of this class. I want to both threads drawing something constantly but only one is able to. Why?

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;

import javax.swing.JPanel;


public class Zegar extends JPanel implements Runnable {

	/**
	 * 
	 */
	private static final long serialVersionUID = -6558753218893814612L;
	Color kolor;
	double wsk_x1, wsk_y1,wsk_x2,wsk_y2;
	long t;
	int n=0;
	

	int width, height;
	Zegar(){
		this.setPreferredSize(new Dimension(300,300));
		t=1000;
		
		
	}
	Zegar(long t){
		this.setPreferredSize(new Dimension(300,300));
		this.t=t;
		width = getWidth();
		height = getHeight();
	}
	
	public void rysujwskazowke(){
		double ck=0;
		double sk=0;
		double alfa = 0, beta = 0;
		while(true){	
			wsk_x1=width/2;
			wsk_y1=height/2;
			alfa=alfa+2*Math.PI/60;
			beta=alfa;//-Math.PI/2;
			
			if(beta>0 && beta<Math.PI/2){
				ck=-20;
				sk=-20;
			}
			if(beta>Math.PI/2 && beta<Math.PI){
				ck=20;
				sk=-20;
			}
			if(beta>Math.PI && beta<3*Math.PI/2){
				ck=20;
				sk=20;
			}
			if(beta>3*Math.PI/2 && beta<2*Math.PI){
				ck=-20;
				sk=20;
			}

			wsk_x2=width/2+(Math.cos(beta)*width/2+ck);
			wsk_y2=height/2+(Math.sin(beta)*height/2+sk);
			try {
				Thread.sleep(t);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			if(alfa>2*Math.PI){
				alfa=0;
			}
			this.repaint();
		}
	}
	public void paint(Graphics g){
		super.paintComponent(g);
		width = getWidth();
	    height = getHeight();

		g.setColor(Color.white);
		g.fillOval(10, 10, width-20, height-20);
		g.setColor(Color.black);
		g.drawLine((int)wsk_x1, (int)wsk_y1,(int)wsk_x2,(int)wsk_y2);
			
	}
	public void run() {
		
		while (true){
			rysujwskazowke();
		}	
	}

}

import java.awt.Color;
import java.awt.Dimension;
import java.awt.FlowLayout;

import javax.swing.BorderFactory;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;


public class Zegary extends JPanel {

	/**
	 * 
	 */
	private static final long serialVersionUID = -4828549146735079562L;
	static Zegar zegar1=new Zegar(500);
	static Zegar zegar2=new Zegar(500);
	
	public Zegary(){
		super(new FlowLayout());
		zegar1.setBackground(Color.BLUE);
		add(zegar1);
		zegar2.setBackground(Color.GREEN);
		add(zegar2);

		setPreferredSize(new Dimension(700, 820));
        setBorder(BorderFactory.createCompoundBorder(
                                BorderFactory.createMatteBorder(
                                                1,1,2,2,Color.black),
                                BorderFactory.createEmptyBorder(5,5,5,5)));
	}
	private static void stworzipokazGUI() {
        JFrame frame = new JFrame("Zegarki");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JComponent newContentPane = new Zegary();
        newContentPane.setOpaque(true);
        frame.setContentPane(newContentPane);

        frame.pack();
        frame.setVisible(true);
    }
	public static void main(String args[]){
		javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
            	stworzipokazGUI();
            }
        });
		zegar1.run();
		zegar2.run();

	}
}

[Fubarable]

What type of background thread will you get with this?

      zegar1.run(); // calls run method directly. No background thread created.
      zegar2.run();

How about with this?

      //zegar1.run();
      //zegar2.run();

      // create two Threads, feed them with the Runnables and start the threads.
      new Thread(zegar1).start();
      new Thread(zegar2).start();

Also there are several other issues with your code including drawing in a paint method rather than a paintComponent method and inappropriate use of static (most all statics should be removed from your code).

[przenica]

What about JPanels? How can i add objects of class Zegary to the contentPane?

[Fubarable]

What about JPanels? How can i add objects of class Zegary to the contentPane?

This question confuses me. How do you add JPanels to a contentPane? You can simply add them, such as via getContentPane().add(myJPanel). What problems are you having? Are you confident in the use of layout managers?