案例分析

  • 案例1

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    public class JoinTest1  extends  Thread{
     
     
        public void run(){
            System.out.println(Thread.currentThread().getName()+":begin");
            try {
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName()+":end");
        }
     
     
        public static void main(String[] args) throws InterruptedException {
            JoinTest1 joinTest1 = new JoinTest1();
            joinTest1.setName("childThread");
            long a = System.currentTimeMillis();
            joinTest1.start();
     
            joinTest1.join();
            long b = System.currentTimeMillis();
     
            System.out.println("等待时间:"+(b-a));
            System.out.println("end----------------");
     
        }
    }

    执行结果：

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    childThread:begin
    childThread:end
    等待时间:2003
    end----------------
     
    Process finished with exit code 0

    主线程等待子线程睡眠2秒钟之后继续执行，结果没有问题

  • 案例2

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    public class JoinTest2 extends  Thread{
     
     
        public void run(){
            System.out.println(Thread.currentThread().getName()+":begin");
            try {
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName()+":end");
        }
     
     
        public static void main(String[] args) throws InterruptedException {
            JoinTest2 joinTest2 = new JoinTest2();
            joinTest2.setName("childThread");
            long a = System.currentTimeMillis();
            joinTest2.start();
     
            joinTest2.join(500);
            long b = System.currentTimeMillis();
     
            System.out.println("等待时间:"+(b-a));
            System.out.println("end----------------");
     
        }
    }

    执行结果：

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    childThread:begin
    等待时间:501
    end----------------
    childThread:end
     
    Process finished with exit code 0

    join(long millis)的方法在时间到了之后结束了等待，主线程继续执行

  • 案例3

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    public class JoinTest3 extends  Thread{
     
     
        public void run(){
            System.out.println(Thread.currentThread().getName()+":begin");
            try {
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName()+":end");
        }
     
     
        public static void main(String[] args) throws InterruptedException {
            JoinTest3 joinTest3 = new JoinTest3();
            joinTest3.setName("childThread");
            long a = System.currentTimeMillis();
            joinTest3.start();
     
            joinTest3.join(5000);
            long b = System.currentTimeMillis();
     
            System.out.println("等待时间:"+(b-a));
            System.out.println("end----------------");
     
        }
    }

    执行结果：

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    childThread:begin
    childThread:end
    等待时间:2005
    end----------------
     
    Process finished with exit code 0