JAVA主线程等待子线程全部结束

public class TestMethod {/** * @param args */public static void main(String[] args) {List<Thread> list = new ArrayList<Thread>();for(int i =0;i<100;i++){Out out = new Out();Thread t = new Thread(out);list.add(t);t.start();}for(int i = 0;i<list.size();i++){Thread t = list.get(i);try {t.join();} catch (InterruptedException e) {e.printStackTrace();}}System.out.println("all over!");}}class Out implements Runnable{public void run() {System.out.println(Thread.currentThread().getName()+" begin");try {Thread.sleep(100);} catch (InterruptedException e) {e.printStackTrace();}}}