线程

class Thread implements Runnable {
    /* Make sure registerNatives is the first thing <clinit> does. */
    private static native void registerNatives();
    static {
        registerNatives();
    }

package mythread;

public class MyThread1 extends Thread
{
   private String name;
   public MyThread1(String name)
   {
       this.name = name;
   }
    public void run()
    {
        System.out.println("hello " + name);
    }
    public static void main(String[] args)
    {
        Thread thread = new MyThread1("world");
      thread.start();
   }
}

package mythread;

public class MyThread2 implements Runnable

{
    private String name;
    public void setName(String name)
    {

        this.name = name;
    }
    public void run()
   {
       System.out.println("hello " + name);
    }

    public static void main(String[] args)
    {
         MyThread2 myThread = new MyThread2();
         myThread.setName("world");
         Thread thread = new Thread(myThread);
          thread.start();

   }

}

  private volatile boolean go = false;
    public static void main(String args[]) throws InterruptedException {
        final NotificationDemo test = new NotificationDemo();

        Runnable waitTask = new Runnable(){

            @Override
            public void run(){
                try {
                    test.shouldGo();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println(Thread.currentThread().getName() + " finished Execution");
            }
        };

        Runnable notifyTask = new Runnable(){

            @Override
            public void run(){
                test.go();
                System.out.println(Thread.currentThread().getName() + " finished Execution");
            }
        };

        Thread t1 = new Thread(waitTask, "WT1"); //will wait
        Thread t2 = new Thread(waitTask, "WT2"); //will wait
        Thread t3 = new Thread(waitTask, "WT3"); //will wait
        Thread t4 = new Thread(notifyTask,"NT1"); //will notify

        //starting all waiting thread
        t1.start();
        t2.start();
        t3.start();

        //pause to ensure all waiting thread started successfully
        Thread.sleep(200);

        //starting notifying thread
        t4.start();

    }
    /*
     * wait and notify can only be called from synchronized method or bock
     */
    private synchronized void shouldGo() throws InterruptedException {
        while(go != true){
            System.out.println(Thread.currentThread()
                    + " is going to wait on this object");
            wait(); //release lock and reacquires on wakeup
            System.out.println(Thread.currentThread() + " is woken up");
        }
        go = false; //resetting condition
    }

    /*
     * both shouldGo() and go() are locked on current object referenced by "this" keyword
     */
    private synchronized void go() {
        while (go == false){
            System.out.println(Thread.currentThread()
                    + " is going to notify all or one thread waiting on this object");

            go = true;   //making condition true for waiting thread
            notify();  // only one out of three waiting thread WT1, WT2,WT3 will woke up
            //notifyAll(); // all waiting thread  WT1, WT2,WT3 will woke up
        }

    }

Thread[WT2,5,main] is going to wait on this object
Thread[WT1,5,main] is going to wait on this object
Thread[WT3,5,main] is going to wait on this object
Thread[NT1,5,main] is going to notify all or one thread waiting on this object
NT1 finished Execution
Thread[WT2,5,main] is woken up
WT2 finished Execution

Thread.yield(); 对锁没有影响  并不会让出锁

public static void main(String[] args) throws InterruptedException {
    Runnable interruptTask = new Runnable() {
        @Override
        public void run() {
            int i = 0;
            try {
                //在正常运行任务时，经常检查本线程的中断标志位，如果被设置了中断标志就自行停止线程
                while (!Thread.currentThread().isInterrupted()) {
                    Thread.sleep(100); // 休眠100ms
                    i++;
                    System.out.println(Thread.currentThread().getName() + " (" + Thread.currentThread().getState() + ") loop " + i);
                }
            } catch (InterruptedException e) {
                //在调用阻塞方法时正确处理InterruptedException异常。（例如，catch异常后就结束线程。）
                System.out.println(Thread.currentThread().getName() + " (" + Thread.currentThread().getState() + ") catch InterruptedException.");
            }
        }
    };
    Thread t1 = new Thread(interruptTask, "t1");
    System.out.println(t1.getName() +" ("+t1.getState()+") is new.");

    t1.start();                      // 启动“线程t1”
    System.out.println(t1.getName() +" ("+t1.getState()+") is started.");

    // 主线程休眠300ms，然后主线程给t1发“中断”指令。
    Thread.sleep(300);
    t1.interrupt();
    System.out.println(t1.getName() +" ("+t1.getState()+") is interrupted.");

    // 主线程休眠300ms，然后查看t1的状态。
    Thread.sleep(300);
    System.out.println(t1.getName() +" ("+t1.getState()+") is interrupted now.");
}

public class HasSelfPrivateNum {
    
    public void addI(String username)
    {
        try
        {
            int num = 0;
            if(username.equals("a"))
            {
                num = 100;
                System.out.println("a set over !");
                Thread.sleep(2000);
            }
            else
            {
                num = 200;
                System.out.println("b set over !");
            }
            System.out.println(username + " num = " + num);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}