java线程控制，当stop按钮就停止，当start按钮就开始运行，当按stop时程序又停止的实现方法

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);
			} catch (InterruptedException e) {
			}
			System.out.println("this is a test!");
		}
	}

}