Java thread control, when the Stop button is stopped, when the Start button starts running, the implementation method stops when the stop is pressed

Package Test;
Import Java.awt.FlowLayout;
Import java.awt.event.ActionEvent;

Import Java.awt.event.ActionListener;
Import Javax.swing.JButton;
Import Javax.swing.JFrame;

Import Javax.swing.JPanel;

	public Class A extends JFrame {shethread thread = null;
			Public A () {try {createframe ();
		catch (Exception e) {e.printstacktrace ();
		} private void Createframe () {JPanel JP = new JPanel (new FlowLayout ());

		This.add (JP);
		JButton Jbstart = new JButton ("Start");
		JButton jbend = new JButton ("Stop");
		Jp.add (Jbstart);

		Jp.add (Jbend);
		This.setsize (300, 100);
		This.setvisible (TRUE);
		This.setresizable (FALSE);

		This.setdefaultcloseoperation (Jframe.exit_on_close);
					Jbstart.addactionlistener (new ActionListener () {public void actionperformed (ActionEvent e) {if (thread!= null)
				Thread.stop ();
				thread = new Shethread ();
			Thread.Start ();
		}
		}); Jbend.addactionlistener (new ActionListener () {public void actionperformed (ActionEvent e) {if (thread!= null) thread.stop ();
			thread = NULL;
	}
		});
	public static void Main (string[] args) {new A (). Show (); Class Shethread extends Thread {public shethread () {} public void run () {while (true) {try {sleep (
			1000);
		The catch (Interruptedexception e) {} System.out.println ("This is a test!"); }
	}

}