Usage instance resolution of Java methods in Java multithreading

On the first code

Create a new Thread, the code is as follows:

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();
  }
}

Then create a new test class. The code is as follows:

package com.thread.test;
/*
 * 0-50 This is the main thread ,50-100 Execution is A thread , And will be A The main thread does not continue until the thread is fully executed 
 */
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(" The main thread "+"["+i+"]");
    }
  }
}

The Join method in Thread is explained in Java Platform SE8 API as follows:

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.

On the first code

Create a new Thread, the code is as follows:

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();
  }
}

Then create a new test class. The code is as follows:

package com.thread.test;
/*
 * 0-50 This is the main thread ,50-100 Execution is A thread , And will be A The main thread does not continue until the thread is fully executed 
 */
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(" The main thread "+"["+i+"]");
    }
  }
}

The Join method in Thread is explained in Java Platform SE8 API as follows:

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.

My own understanding is that a thread that USES the join method will be forced in and the other threads will wait until the thread is fully executed.