Java 判断线程池所有任务是否执行完毕的操作

import java.util.concurrent.ExecutorService; 
import java.util.concurrent.Executors; 
 
public class Test { 
  public static void main(String args[]) throws InterruptedException { 
    ExecutorService exe = Executors.newFixedThreadPool(3); 
    for (int i = 1; i <= 5; i++) { 
      exe.execute(new SubThread(i)); 
    } 
    exe.shutdown(); 
    while (true) { 
      if (exe.isTerminated()) { 
        System.out.println("结束了！"); 
        break; 
      } 
      Thread.sleep(200); 
    } 
  } 
} 

public class SubThread extends Thread{ 
  private final int i; 
  public SubThread(int i){ 
    this.i = i; 
  } 
  @Override 
  public void run(){ 
    System.out.println(i); 
  } 
}

package com.jd.basic.pk.manager;
import java.lang.reflect.Field;
import java.security.Permission;

public class UseReflection {
  static {
    try {
      System.setSecurityManager(new MySecurityManager());
    } catch (SecurityException se) {
      System.out.println("SecurityManager already set!");
    }
  }

  public static void main(String args[]) {
    Object prey = new Prey();
    try {
      Field pf = prey.getClass().getDeclaredField("privateString");
      pf.setAccessible(true);
      pf.set(prey, "Aminur test");
      System.out.println(pf.get(prey));
    } catch (Exception e) {
      System.err.println("Caught exception " + e.toString());
    }
  }
}

class Prey {
  @SuppressWarnings("unused")
  private String privateString = "privateValue";
}

class MySecurityManager extends SecurityManager {
  public void checkPermission(Permission perm) {
    if (perm.getName().equals("suppressAccessChecks")) {
      throw new SecurityException("Can not change the permission dude.!");
    }
  }
}