先上代码

新建一个Thread,代码如下:

package com.thread.test;

public class MyThread extends Thread {

private String name;

public MyThread(String name) {

this.name = name;

}

@Override

public void run() {

for (int i = 0; i < 100; i++) {

System.out.println(name+"["+i+"]");

}

super.run();

}

}

之后新建测试类,代码如下:

package com.thread.test;

/*

* 0-50执行的是主线程,50-100执行的是A线程,并且将A线程完全执行完后才继续执行主线程

*/

public class ThreadDemo{

public static void main(String[] args) {

MyThread t = new MyThread("A");

t.start();

for (int i = 0; i < 100; i++) {

if (i>50) {

try {

t.join();

} catch (InterruptedException e) {

e.printStackTrace();

}

}

System.out.println("主线程"+"["+i+"]");

}

}

}

下面是Java Platform SE8 API中对Thread中Join方法的解释:

public final void join(long millis)

throws InterruptedExceptionWaits at most millis milliseconds for this thread to die. A timeout of 0 means to wait forever.

This implementation uses a loop of this.wait calls conditioned on this.isAlive. As a thread terminates the this.notifyAll method is invoked. It is recommended that applications not use wait, notify, or notifyAll on Thread instances.

Parameters:

millis - the time to wait in milliseconds

Throws:

IllegalArgumentException - if the value of millis is negative

InterruptedException - if any thread has interrupted the current thread. The interrupted status of the current thread is cleared when this exception is thrown.

先上代码

新建一个Thread,代码如下:

package com.thread.test;

public class MyThread extends Thread {

private String name;

public MyThread(String name) {

this.name = name;

}

@Override

public void run() {

for (int i = 0; i < 100; i++) {

System.out.println(name+"["+i+"]");

}

super.run();

}

}

之后新建测试类,代码如下:

package com.thread.test;

/*

* 0-50执行的是主线程,50-100执行的是A线程,并且将A线程完全执行完后才继续执行主线程

*/

public class ThreadDemo{

public static void main(String[] args) {

MyThread t = new MyThread("A");

t.start();

for (int i = 0; i < 100; i++) {

if (i>50) {

try {

t.join();

} catch (InterruptedException e) {

e.printStackTrace();

}

}

System.out.println("主线程"+"["+i+"]");

}

}

}

下面是Java Platform SE8 API中对Thread中Join方法的解释:

public final void join(long millis)

throws InterruptedExceptionWaits at most millis milliseconds for this thread to die. A timeout of 0 means to wait forever.

This implementation uses a loop of this.wait calls conditioned on this.isAlive. As a thread terminates the this.notifyAll method is invoked. It is recommended that applications not use wait, notify, or notifyAll on Thread instances.

Parameters:

millis - the time to wait in milliseconds

Throws:

IllegalArgumentException - if the value of millis is negative

InterruptedException - if any thread has interrupted the current thread. The interrupted status of the current thread is cleared when this exception is thrown.

我自己的理解就是会强行进入使用join方法的线程，其他线程等待该线程完全执行完后才会进来。