Java ThreadGroup list() 方法及示例

 Java ThreadGroup 类

说明

Java ThreadGroup list() 方法将有关此线程组的信息打印到标准输出。这仅对调试有用。

声明

以下是java.lang.ThreadGroup.list()方法的声明

public void list() 

参数

无

返回值

此方法不返回任何值。

异常

无

示例 1

以下示例显示了在单个 ThreadGroup 对象的情况下 ThreadGroup list() 方法的用法。我们创建了一个 ThreadGroup 对象并为其分配了一个名称。然后我们使用之前创建的线程组对象创建了两个线程。使用list()方法，我们获取该线程组对象的信息。

package com.yxjc123;

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

   public void start() {
      try {     
         //创建一个ThreadGroup
         ThreadGroup threadGroup = new ThreadGroup("ThreadGroup");

         //创建一个线程
         Thread t1 = new Thread(threadGroup, this);
         System.out.println("Starting " + t1.getName() + "...");
         t1.start();
            
         //创建另一个线程
         Thread t2 = new Thread(threadGroup, this);
         System.out.println("Starting " + t2.getName() + "...");
         t2.start();

         //打印线程组的详细信息
         threadGroup.list();

         // 阻塞直到其他线程完成
         t1.join();
         t2.join();        


      } catch (InterruptedException ex) {
         System.out.println(ex.toString());
      }
   }

   // 实现 run()
   public void run() {

      for(int i = 0; i < 4;i++) {
         i++;
         try {
			Thread.sleep(50);
		} catch (InterruptedException e) {
			// TODO 自动生成的 catch 块
			e.printStackTrace();
		}
      }
      System.out.println(Thread.currentThread().getName() + " finished executing.");
   }
} 

输出

让我们编译并运行上面的程序，这将产生以下结果

Starting Thread-0...
Starting Thread-1...
java.lang.ThreadGroup[name=ThreadGroup,maxpri=10]
    Thread[Thread-0,5,ThreadGroup]
    Thread[Thread-1,5,ThreadGroup]
Thread-1 finished executing.
Thread-0 finished executing. 

示例 2

以下示例显示了在多个 ThreadGroup 对象的情况下 ThreadGroup list() 方法的用法。我们创建了一个 ThreadGroup 对象并为其分配了一个名称。接下来，我们创建了一个子 ThreadGroup 对象。然后我们使用之前创建的线程组对象创建了两个线程。使用 list() 方法，我们打印每个线程组对象的详细信息。

package com.yxjc123;

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

   public void start() {
      try {     
         //创建父ThreadGroup
         ThreadGroup pThreadGroup = new ThreadGroup("parent ThreadGroup");
		 
         //为父ThreadGroup创建子ThreadGroup
         ThreadGroup cThreadGroup = new ThreadGroup(pThreadGroup, "child ThreadGroup");

         //创建一个线程
         Thread t1 = new Thread(pThreadGroup, this);
         System.out.println("Starting " + t1.getName() + "...");
         t1.start();
            
         //创建另一个线程
         Thread t2 = new Thread(cThreadGroup, this);
         System.out.println("Starting " + t2.getName() + "...");
         t2.start();

         //打印线程组的详细信息
         pThreadGroup.list();
         cThreadGroup.list();
         
         // 阻塞直到其他线程完成
         t1.join();
         t2.join();

      } catch (InterruptedException ex) {
         System.out.println(ex.toString());
      }
   }

   // 实现 run()
   public void run() {

      for(int i = 0; i < 4;i++) {
         i++;
         try {
			Thread.sleep(50);
		} catch (InterruptedException e) {
			// TODO 自动生成的 catch 块
			e.printStackTrace();
		}
      }
      System.out.println(Thread.currentThread().getName() + " finished executing.");
   }
} 

输出

让我们编译并运行上面的程序，这将产生以下结果 -

Starting Thread-0...
Starting Thread-1...
java.lang.ThreadGroup[name=parent ThreadGroup,maxpri=10]
    Thread[Thread-0,5,parent ThreadGroup]
    java.lang.ThreadGroup[name=child ThreadGroup,maxpri=10]
        Thread[Thread-1,5,child ThreadGroup]
java.lang.ThreadGroup[name=child ThreadGroup,maxpri=10]
    Thread[Thread-1,5,child ThreadGroup]
Thread-0 finished executing.
Thread-1 finished executing. 

示例 3

以下示例显示了 ThreadGroup list() 方法在子 ThreadGroup 对象和孙 ThreadGroup 对象的情况下的用法。我们创建了一个 ThreadGroup 对象并为其分配了一个名称。接下来，我们创建了一个子 ThreadGroup 对象。然后，我们使用之前创建的子线程组对象和孙线程组对象创建了两个线程。使用 list() 方法，我们打印每个线程组对象的父级名称。

package com.yxjc123;

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

   public void start() {
      try {     
         //创建父ThreadGroup
         ThreadGroup pThreadGroup = new ThreadGroup("Parent ThreadGroup");
		 
         //为父ThreadGroup创建子ThreadGroup
         ThreadGroup cThreadGroup = new ThreadGroup(pThreadGroup, "Child ThreadGroup");
		 
         //为父ThreadGroup创建孙ThreadGroup
         ThreadGroup gThreadGroup = new ThreadGroup(cThreadGroup, "GrandChild ThreadGroup");

         //创建一个线程
         Thread t1 = new Thread(cThreadGroup, this);
         System.out.println("Starting " + t1.getName() + "...");
         t1.start();
            
         //创建另一个线程
         Thread t2 = new Thread(gThreadGroup, this);
         System.out.println("Starting " + t2.getName() + "...");
         t2.start();
            
         //打印线程组的详细信息
         pThreadGroup.list();
         cThreadGroup.list();
         gThreadGroup.list();

         // 阻塞直到其他线程完成
         t1.join();
         t2.join();
      } catch (InterruptedException ex) {
         System.out.println(ex.toString());
      }
   }

   // 实现 run()
   public void run() {

      for(int i = 0; i < 4;i++) {
         i++;
         try {
			Thread.sleep(50);
		} catch (InterruptedException e) {
			// TODO 自动生成的 catch 块
			e.printStackTrace();
		}
      }
      System.out.println(Thread.currentThread().getName() + " finished executing.");
   }
} 

输出

让我们编译并运行上面的程序，这将产生以下结果−

Starting Thread-0...
Starting Thread-1...
java.lang.ThreadGroup[name=Parent ThreadGroup,maxpri=10]
    java.lang.ThreadGroup[name=Child ThreadGroup,maxpri=10]
        Thread[Thread-0,5,Child ThreadGroup]
        java.lang.ThreadGroup[name=GrandChild ThreadGroup,maxpri=10]
            Thread[Thread-1,5,GrandChild ThreadGroup]
java.lang.ThreadGroup[name=Child ThreadGroup,maxpri=10]
    Thread[Thread-0,5,Child ThreadGroup]
    java.lang.ThreadGroup[name=GrandChild ThreadGroup,maxpri=10]
        Thread[Thread-1,5,GrandChild ThreadGroup]
java.lang.ThreadGroup[name=GrandChild ThreadGroup,maxpri=10]
    Thread[Thread-1,5,GrandChild ThreadGroup]
Thread-1 finished executing.
Thread-0 finished executing.