Thread中join()

（1）作用

               实际上就是等待子线程执行完，主线程后面的代码才能执行（相当于wait）

（2）实例

               1.未使用join

import java.util.concurrent.TimeUnit;

public class JoinTest {
	public static void main(String[] args) {
		Thread thread = new Thread(new Runnable() {
			
			public void run() {
				try {
					TimeUnit.SECONDS.sleep(1);
				} catch (InterruptedException e) {
					e.printStackTrace();
				}
				System.out.println("sub thread "+Thread.currentThread().getName()+" end");
			}
		});
		thread.start();

		System.out.println("main thread end;");
	}
}

        结果为：（不一定一直是这样）

main thread end;
sub thread Thread-0 end

       也就是说：主线程执行结束了，子线程才结束

               2.使用join

import java.util.concurrent.TimeUnit;

public class JoinTest {
	public static void main(String[] args) {
		Thread thread = new Thread(new Runnable() {
			
			public void run() {
				try {
					TimeUnit.SECONDS.sleep(1);
				} catch (InterruptedException e) {
					e.printStackTrace();
				}
				System.out.println("sub thread "+Thread.currentThread().getName()+" end");
			}
		});
		thread.start();
		try {
			thread.join();//等待线程执行完
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		System.out.println("main thread end;");
	}
}

      结果一定为：

sub thread Thread-0 end
main thread end;