Communication notes between threads

Communication notes between threads

1. Work on thread A and then thread B

   Idea: To use an object lock, A first occupies the object lock, and then releases it to B after use

   public class Test {
         
         
       private static Object lock = new Object();
       static class ThreadA implements Runnable {
         
         
           @Override
           public void run() {
         
         
               synchronized (lock) {
         
         
                   for (int i = 0; i < 100; i++) {
         
         
                       System.out.println("Thread A " + i);
                   }
               }
           }
       }
       static class ThreadB implements Runnable {
         
         
           @Override
           public void run() {
         
         
               synchronized (lock) {
         
         
                   for (int i = 0; i < 100; i++) {
         
         
                       System.out.println("Thread B " + i);
                   }
               }
           }
       }
       public static void main(String[] args) throws InterruptedException {
         
         
           new Thread(new ThreadA()).start();
           new Thread(new ThreadB()).start();
       }
   }
   

2. A thread prints even numbers, B thread prints odd numbers

   Idea: Use volatile+synchronized, because a++ is not an atomic operation, it needs to be locked

   public class Test {
         
         
       private static Object lock = new Object();
       private static volatile int a = 0;
       static class ThreadA implements Runnable {
         
         
           @Override
           public void run() {
         
         
               while(a<100){
         
         
                   if(a%2==1){
         
         
                       try {
         
         
                           System.out.println("ThreadA: " + a);
                           synchronized (lock){
         
         
                               a++;
                           }
                       } catch (Exception e) {
         
         
                           e.printStackTrace();
                       }
                   }
               }
           }
       }
       static class ThreadB implements Runnable {
         
         
           @Override
           public void run() {
         
         
               while(a<100){
         
         
                   if(a%2==0){
         
         
                       try {
         
         
                           System.out.println("ThreadB: " + a);
                           synchronized (lock){
         
         
                               a++;
                           }
                       } catch (Exception e) {
         
         
                           e.printStackTrace();
                       }
                   }
               }
           }
       }
       public static void main(String[] args) {
         
         
           new Thread(new ThreadA()).start();
           new Thread(new ThreadB()).start();
       }
   }