Implementation of inter-thread communication wait () and notify () methods

Java provides 3 very important ways to skillfully solve communication problems between threads. These 3 methods are: Wait (), notify (), and Notifyall (). They are all the final methods of the object class, so each class has them by default.

Although all classes have these 3 methods by default, they are only meaningful if the Synchronized keyword is scoped to the same synchronization problem and is used in conjunction with the 3 methods.

• If the object calls the wait method, it causes the thread holding the object to hand over the object's control and then waits.

• If an object calls the Notify method, it notifies a thread that is waiting for control of the object to continue running.

• If the object calls the Notifyall method, all threads waiting for control of the object will be notified to continue running.

This is illustrated by an example of 2 threads, which alternately print a, B

package com.smart.concurrency.chapter2;/** *  @Description   *  @author   Gaowenming */public class waitandnotifytest {    public static  final object obj = new object ();     public static  void main (String[] args)  throws Exception {         thread t0 = new thread (New thread0 ());         thread t1 = new thread (New thread1 ());         t0.start ();         t1.start ();     }}class Thread0 implements Runnable {     @Override      public void run ()  {        while   (True)  {    &Nbsp;       synchronized  (waitandnotifytest.obj)  {                 try {                      Thread.Sleep (;               )      system.out.println ("A");                     waitandnotifytest.obj.notify ();                      WaitAndNotifyTest.obj.wait ();                 } catch  (exception e)  {              &Nbsp;      e.printstacktrace ();                 }             }        }    }}class thread1  implements Runnable {     @Override     public void  run ()  {        while  (true)  {             synchronized  (waitandnotifytest.obj)  {                 try {                      thread.sleep (;              )     &nbsP; system.out.println ("B");                     waitandnotifytest.obj.notify ();                     waitandnotifytest.obj.wait ();                }  catch  (exception e)  {                     e.printstacktrace ();                 }             }        }    }}

Code, you can see that 2 threads are monitoring the same object waitandnotifytest.obj to ensure that the synchronization operation is valid

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Implementation of inter-thread communication wait () and notify () methods