Java.lang.ThreadGroup.checkAccess() 方法

描述

java.lang.ThreadGroup.checkAccess() 方法判断当前运行的线程是否有权限修改这个线程组。

声明

以下是 java.lang.ThreadGroup.checkAccess() 方法的声明。

public final void checkAccess()

参数

NA

返回值

此方法不返回任何值。

异常

SecurityException − 如果当前线程不允许访问这个线程组。

示例

下面的例子展示了 java.lang.ThreadGroup.checkAccess() 方法的使用。

package com.tutorialspoint;

import java.lang.*;

public class ThreadGroupDemo implements Runnable {
   public static void main(String[] args) {
      ThreadGroupDemo tg = new ThreadGroupDemo();
      tg.func();
   }

   public void func() {
      try {     
         // create a parent ThreadGroup
         ThreadGroup pGroup = new ThreadGroup("Parent ThreadGroup");
    
         // create a child ThreadGroup for parent ThreadGroup
         ThreadGroup cGroup = new ThreadGroup(pGroup, "Child ThreadGroup");

         // create a thread
         Thread t1 = new Thread(pGroup, this);
         System.out.println("Starting " + t1.getName() + "...");
         t1.start();
            
         // create another thread
         Thread t2 = new Thread(cGroup, this);
         System.out.println("Starting " + t2.getName() + "...");
         t2.start();
            
         // checking the access for these ThreadGroups.
         try {
            pGroup.checkAccess();
            System.out.println(pGroup.getName() + " has access");
            cGroup.checkAccess();
            System.out.println(cGroup.getName() + " has access");
         } catch (SecurityException ex) {
            System.out.println("No access: " + ex.toString());
         }
         // block until the other threads finish
         t1.join();
         t2.join();
      } catch (InterruptedException ex) {
         System.out.println(ex.toString());
      }
   }

   // implements run()
   public void run() {

      for(int i = 0;i<1000;i++) {
         i++;
      }
      System.out.println(Thread.currentThread().getName() + " finished executing");
   }
} 

让我们编译并运行上面的程序，这将产生下面的结果 −

Starting Thread-0...
Starting Thread-1...
Parent ThreadGroup has access
Child ThreadGroup has access
Thread-0 finished executing
Thread-1 finished executing