java.lang.ThreadGroup.checkAccess() 方法確定當前運行的線程是否有權修改該線程組。

聲明

以下是java.lang.ThreadGroup.checkAccess()方法的聲明

public final void checkAccess()

參數

• NA

返回值

此方法不返回任何值。

異常

• SecurityException -- 如果當前線程不允許訪問該線程組。

例子

下麵的例子顯示java.lang.ThreadGroup.checkAccess()方法的使用。

package com.yiibai;

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");
   }
} 

讓我們來編譯和運行上麵的程序，這將產生以下結果：

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