java中join方法的理解与说明详解

public class MyRunnable implements Runnable {
 private int num;
 private String threadName;
 private long result;
 
 public MyRunnable(int num, String threadName) {
  this.threadName = threadName;
  this.num = num;
 }
 
 public void run() {
  for (int i = 0; i < num; i++) {
   result += i;
  }
 }
 
 
 public long getResult() {
  return result;
 }
}

 
public class NormalTest {
 public static void main(String[] args) {
 
  normal();
 
 }
 
 private static void normal() {
  MyRunnable myRunnable_1 = new MyRunnable(1000, "runnable_1");
 
  Thread thread_1 = new Thread(myRunnable_1);
  thread_1.start();
 
  do {
   System.out.println("--------------------------------------------------");
   System.out.println("thread status: " + thread_1.isAlive() + ",result: " + myRunnable_1.getResult());
  } while (thread_1.isAlive());
 }
}

 
public class JoinTest {
 public static void main(String[] args) {
 
  join();
 
 }
 
 
 private static void join() {
 
  MyRunnable myRunnable_1 = new MyRunnable(1000, "runnable_1");
 
  Thread thread_1 = new Thread(myRunnable_1);
  thread_1.start();
 
  try {
   thread_1.join();
  } catch (InterruptedException e) {
   e.printStackTrace();
  }
 
  System.out.println("thread status: " + thread_1.isAlive() + ",result: " + myRunnable_1.getResult());
 
 }
}

 public final synchronized void join(long millis)
 throws InterruptedException {
  long base = System.currentTimeMillis();
  long now = 0;
 
  if (millis < 0) {
   throw new IllegalArgumentException("timeout value is negative");
  }
 
  if (millis == 0) {    // join 方法如果不传参数会默认millis 为 0
   while (isAlive()) {
    wait(0);
   }
  } else {
   while (isAlive()) {
    long delay = millis - now;
    if (delay <= 0) {
     break;
    }
    wait(delay);
    now = System.currentTimeMillis() - base;
   }
  }
 }