java join 多线程顺序执行

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

        final List<Thread> threads = new ArrayList<Thread>();
        for(int i=0;i<100;i++){
            class A extends Thread{
                int i ;
                public A(int i){
                    this.i = i;
                }
                @Override
                public void run() {
                    try {
                        Thread.sleep(100);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println("thread " + i);
                }
            }
            threads.add(new A(i));
        }
        //倒叙
        Collections.reverse(threads);
        
        for(int i=99;i>=0;i--){
            threads.get(i).start();
            if(i!=0){
                threads.get(i).join();
            }
        }
    }

关键点：

1. 线程执行后才能join
2. 先运行后面的。