java 多线程

import java.awt.*;
import java.awt.event.*;
import java.applet.*;
public class Counter1 extends Applet {
    private int count = 0;
    private Button onOff = new Button("Toggle");
    private Button start = new Button("Start");
    private TextFiled t =  new TextFiled(10);
    private boolean runFlag = true;
    private long i = 0;
    public void int() {
        add(t);
        start.addActionListener(new StartL());
        add(start);
        onOff.addActionListener(new onOffL());
        add(onOff);
    }
public void go() {
    while(true) {
        i = 0;
        while(i<=10000000000) i++;
        if(runFlag)    t.setText(Integer.toString(count++));
        }
    }

class StartL implements ActionListener {
    public void actionPerformed(ActionEvent e) {
        go();
    }
}
class onOffL implements ActionListener {
    public void actionPerformed(ActionEvent e){
        runFlag = !runFlag;
    }
}
public static void main(String[] args)/*process interface,not exceut while brower*/
{
    Counter1 applet = new Counter1();
    Frame aFrame = new Frame("Counter1");
    aFrame.addWindowListener(new WindowAdapter(){
        public void windowClosing(WindowEvent e) {
            System.exit(0);
        }
    });
    aFrame.add(applet,BorderLayout.CENTER);
    aFrame.setSize(300,200);
    applet.init();
    applet.start();
    aFrame.setVisible(true);
}
}

运行时，一旦按下start按钮，就会调用go方法，程序不能再对其它任何事件进行响应，Toggle按钮和窗口的关闭按钮不再有反应

我们期望go()继续执行自己的操作，而于此同时，它也需要返回，以便actionPerformed()能够完成，而且用户界面也能继续响应用户操作

即线程的作用