Java - ThreadGroup getParent() 方法

描述

Java ThreadGroup getParent() 方法返回该线程组的父线程组的名称。

声明

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

public final ThreadGroup getParent()

参数

无

返回值

此方法返回此线程组的父级。顶级线程组是唯一父级为 null 的线程组。

异常

无

获取 ThreadGroup 父级的示例

以下示例展示了在单个 ThreadGroup 对象的情况下 ThreadGroup getParent() 方法的使用。我们创建了一个 ThreadGroup 对象并为其分配了一个名称。然后，我们使用前面创建的线程组对象创建了两个线程。使用 getParent() 方法，我们获取了此线程组对象的父级的名称，该名称将为 main。

package com.tutorialspoint;

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

   public void start() {
      try {     
         // create a ThreadGroup
         ThreadGroup threadGroup = new ThreadGroup("ThreadGroup");

         // create a thread
         Thread t1 = new Thread(threadGroup, this);
         System.out.println("Starting " + t1.getName() + "...");
         t1.start();
            
         // create another thread
         Thread t2 = new Thread(threadGroup, this);
         System.out.println("Starting " + t2.getName() + "...");
         t2.start();

         // returns the name of parent of thread group
         String name = threadGroup.getParent().getName();
         System.out.println("Name of parent of the threadGroup = " + name);

         // 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 < 4;i++) {
         i++;
         try {
			Thread.sleep(50);
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
      }
      System.out.println(Thread.currentThread().getName() + " finished executing.");
   }
} 

输出

让我们编译并运行上述程序，这将产生以下结果：

Starting Thread-0...
Starting Thread-1...
Name of parent of the threadGroup = main
Thread-1 finished executing.
Thread-0 finished executing.

在多个 ThreadGroup 对象中获取 ThreadGroup 父级的示例

以下示例展示了在多个 ThreadGroup 对象的情况下 ThreadGroup getParent() 方法的使用。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，我们使用前面创建的线程组对象创建了两个线程。使用 getParent() 方法，我们打印每个线程组对象的父级的名称。

package com.tutorialspoint;

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

   public void start() {
      try {     
         // create a parent ThreadGroup
         ThreadGroup pThreadGroup = new ThreadGroup("parent ThreadGroup");
		 
         // create a child ThreadGroup for parent ThreadGroup
         ThreadGroup cThreadGroup = new ThreadGroup(pThreadGroup, "child ThreadGroup");

         // create a thread
         Thread t1 = new Thread(pThreadGroup, this);
         System.out.println("Starting " + t1.getName() + "...");
         t1.start();
            
         // create another thread
         Thread t2 = new Thread(cThreadGroup, this);
         System.out.println("Starting " + t2.getName() + "...");
         t2.start();

         // returns the name of thread group
         String name = pThreadGroup.getParent().getName();
         System.out.println("Name of parent of pThreadGroup = " + name);

         name = cThreadGroup.getParent().getName();
         System.out.println("Name of parent of cThreadGroup = " + name);
         // 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 < 4;i++) {
         i++;
         try {
			Thread.sleep(50);
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
      }
      System.out.println(Thread.currentThread().getName() + " finished executing.");
   }
} 

输出

让我们编译并运行上述程序，这将产生以下结果：

Starting Thread-0...
Starting Thread-1...
Name of parent of pThreadGroup = main
Name of parent of cThreadGroup = parent ThreadGroup
Thread-0 finished executing.
Thread-1 finished executing.

在子/孙 ThreadGroup 对象中获取 ThreadGroup 父级的示例

以下示例展示了在子线程组和孙线程组对象的情况下 ThreadGroup getParent() 方法的使用。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，我们使用前面创建的子线程组和孙线程组对象创建了两个线程。使用 getParent() 方法，我们打印每个线程组对象的父级的名称。

package com.tutorialspoint;

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

   public void start() {
      try {     
         // create a parent ThreadGroup
         ThreadGroup pThreadGroup = new ThreadGroup("Parent ThreadGroup");
		 
         // create a child ThreadGroup for parent ThreadGroup
         ThreadGroup cThreadGroup = new ThreadGroup(pThreadGroup, "Child ThreadGroup");
		 
         // create a grandchild ThreadGroup for parent ThreadGroup
         ThreadGroup gThreadGroup = new ThreadGroup(cThreadGroup, "GrandChild ThreadGroup");

         // create a thread
         Thread t1 = new Thread(cThreadGroup, this);
         System.out.println("Starting " + t1.getName() + "...");
         t1.start();
            
         // create another thread
         Thread t2 = new Thread(gThreadGroup, this);
         System.out.println("Starting " + t2.getName() + "...");
         t2.start();
            
         // returns the name of the parent of thread group
         String name = pThreadGroup.getParent().getName();
         System.out.println("Name of pThreadGroup = " + name);

         name = cThreadGroup.getParent().getName();
         System.out.println("Name of cThreadGroup = " + name);

         name = gThreadGroup.getParent().getName();
         System.out.println("Name of gThreadGroup = " + name);

         // 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 < 4;i++) {
         i++;
         try {
			Thread.sleep(50);
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
      }
      System.out.println(Thread.currentThread().getName() + " finished executing.");
   }
} 

输出

让我们编译并运行上述程序，这将产生以下结果：

Starting Thread-0...
Starting Thread-1...
Name of pThreadGroup = main
Name of cThreadGroup = Parent ThreadGroup
Name of gThreadGroup = Child ThreadGroup
Thread-1 finished executing.
Thread-0 finished executing.