Java ThreadGroup checkAccess()用法及代码示例

ThreadGroup类checkAccess()方法

• checkAccess() 方法可在java.lang包。
• checkAccess() 方法用于检查当前运行的线程是否具有更新线程组的权限。
• checkAccess() 方法不是静态方法，因此不能通过类名访问(即只能通过类对象访问此方法)。
• checkAccess() 方法是 final 方法，因此它不可重写(即此方法在子类中不可重写)。
• 该方法可能在访问线程组时抛出异常。
  SecurityException：在安全管理器存在时当前线程未被授权访问线程组时的此异常。

用法:

    public final void checkAccess();

参数：

• 此方法不接受任何参数。

返回值：

这个方法的返回类型是void，它不返回任何东西。

例：

// Java program to demonstrate the example of 
// checkAccess () method of ThreadGroup Class.

import java.lang.*;

class CheckAccess extends Thread {
    // Override run() of Thread class
    public void run() {
        String name = Thread.currentThread().getName();
        System.out.println(name + " " + "finish executing");
    }
}

public class Main {
    public static void main(String[] args) {
        CheckAccess ca = new CheckAccess();

        try {
            // We are creating an object of ThreadGroup class
            ThreadGroup tg1 = new ThreadGroup("ThreadGroup 1");
            ThreadGroup tg2 = new ThreadGroup("ThreadGroup 2");

            // We are creating an object of Thread class and 
            // we are assigning the ThreadGroup of both the thread

            Thread th1 = new Thread(tg1, ca, "First Thread");
            Thread th2 = new Thread(tg2, ca, "Second Thread");

            // Calling start() method with Thread class object 
            // of Thread class

            th1.start();
            th2.start();

            // Here we are checking access of ThreadGroup
            try {
                tg1.checkAccess();
                System.out.println(tg1.getName() + " " + "has access");

                tg2.checkAccess();
                System.out.println(tg2.getName() + " " + "has access");

            } catch (SecurityException se) {

                System.out.println(se.getMessage());
            }

            th1.join();
            th2.join();

        } catch (Exception ex) {

            System.out.println(ex.getMessage());
        }
    }
}

输出

E:\Programs>javac Main.java
E:\Programs>java Main
ThreadGroup 1 has access
ThreadGroup 2 has access
First Thread finish executing
Second Thread finish executing