2020-10-26 多线程学习1

join关键字 测试:

public class TestJoin {

    public static void main(String[] args) throws InterruptedException {

        // TODO Auto-generated method stub

        for (int i = 0; i < 3; i++) {
            ThreadTest t1=new ThreadTest("A");
            ThreadTest t2=new ThreadTest("B");
            ThreadTest t3=new ThreadTest("C");
            t1.start();
            t3.start();
            t1.join();
            t3.join();
            t2.start();
        }

    }


}
class ThreadTest extends Thread {
    private String name;
    public ThreadTest(String name){
        this.name=name;
    }
    public void run(){
        for(int i=1;i<=1;i++){
            System.out.print(name);
        }
    }
}

打印测试结果为: ACBCABCAB

说明 A/C 由于加入了join关键字,一定先于B执行,而A/C顺序,看cpu调度,无法确定

当: join 关键字后置的时候

public class TestJoin {

    public static void main(String[] args) throws InterruptedException {

        // TODO Auto-generated method stub

        for (int i = 0; i < 3; i++) {
            ThreadTest t1=new ThreadTest("A");
            ThreadTest t2=new ThreadTest("B");
            ThreadTest t3=new ThreadTest("C");
            t1.start();
            t3.start();
            t2.start();

            t1.join();
            t3.join();
        }

    }


}
class ThreadTest extends Thread {
    private String name;
    public ThreadTest(String name){
        this.name=name;
    }
    public void run(){
        for(int i=1;i<=1;i++){
            System.out.print(name);
        }
    }
}

打印结果: ACBBCAACB
多数情况为正确的,但是有错误出现(BCA),说明join关键字使用的时候,应规范使用,放在本身start方法之后(紧挨着)最为妥当.