join（）一个实例来说明

旧城等待， 2022-09-23 08:23 73阅读 0赞

Java Thread join():本函数用来使线程暂停，转让控制权，这里的暂停指的是暂停当前，转让给x.join(),x

方便的理解记忆：join();----老衲加入了！！！！老衲现在最大，或者老衲在规定的时间最大！！我有控制权。

具体看例子：

package com.journaldev.threads;
    
    public class ThreadJoinExample {
    
        public static void main(String[] args) {
            Thread t1 = new Thread(new MyRunnable(), "t1");
            Thread t2 = new Thread(new MyRunnable(), "t2");
            Thread t3 = new Thread(new MyRunnable(), "t3");
            
            t1.start();
            
            //start second thread after waiting for 2 seconds or if it's dead
            try {
                t1.join(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            
            t2.start();
            
            //start third thread only when first thread is dead
            try {
                t1.join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            
            t3.start();
            
            //let all threads finish execution before finishing main thread
            try {
                t1.join();
                t2.join();
                t3.join();
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            
            System.out.println("All threads are dead, exiting main thread");
        }
    
    }
    
    class MyRunnable implements Runnable{
    
        @Override
        public void run() {
            System.out.println("Thread started:::"+Thread.currentThread().getName());
            try {
                Thread.sleep(4000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("Thread ended:::"+Thread.currentThread().getName());
        }
        
    }

**结果：**

Thread started:::t1//t1.join(2000);t1线程获得控制权力，时间2S;----所以t1start----- Thread.sleep(4000);----超过时间交出控制权

Thread started:::t2//------回到主线程----t2 start ----------执行t1.join()-----t1加入，重获新生！！！！-----回到run()继续执行-----输出t1 end----死亡---返回主线程  
Thread ended:::t1  
Thread started:::t3//此刻t3.start();  
Thread ended:::t2//\-----t1,t2，t3---依次join()------t1已经亡，轮到t2-----t2继续上次执行，run()---t2 end-----  
Thread ended:::t3//\-同理t3------交给main----main end  
All threads are dead, exiting main thread