7先1后的线程

public class test {
    private static final int THREAD_COUNT_NUM = 7;
    private static CountDownLatch latch = new CountDownLatch(THREAD_COUNT_NUM);

    public static void main(String[] args) throws InterruptedException {
        for (int i=1;i<=THREAD_COUNT_NUM ;++i){
            int i1 =i;//1.8中可以不用 默认即为常量

            new Thread(() ->{//()->是在jdk8中新出现的一种写法，叫做lambda表达式 替代原来的Runnable接口的匿名内部类

                try {
                    System.out.println("第"+i1+"个龙珠已集到");
                    System.out.println(new Random().nextDouble());
                    Thread.sleep(new Random().nextInt(10000));
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }

                latch.countDown();//当前的线程数减一
            }).start();
            Thread.sleep(2000);
        }
        latch.await();//当所有的线程都执行完，才执行
        System.out.println("神龙升天");
    }
}