Java - ThreadGroup enumerate(Thread[] list) 方法

描述

Java ThreadGroup enumerate(Thread[] list) 方法將此執行緒組及其子組中的每個活動執行緒複製到指定的陣列中。

宣告

以下是 java.lang.ThreadGroup.enumerate(Thread[] list) 方法的宣告

public int enumerate(Thread[] list)

引數

list − 這是要將執行緒列表放入的陣列。

返回值

此方法返回放入陣列中的執行緒數。

異常

SecurityException − 如果當前執行緒沒有許可權列舉此執行緒組。

列舉 ThreadObject 物件列表示例

以下示例展示了在單個 ThreadGroup 物件的情況下使用 ThreadGroup enumerate(Thread[] list) 方法。我們建立了一個 ThreadGroup 物件併為其分配了一個名稱。然後，我們使用前面建立的執行緒組物件建立了兩個執行緒。使用 enumerate() 方法，我們將所有活動執行緒放入陣列中，然後使用 for 迴圈在陣列上列印它們的名稱。

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 number of threads put into the array
         Thread[] list = new Thread[threadGroup.activeCount()];
         int count = threadGroup.enumerate(list);
         for (int i = 0; i < count; i++) {
            System.out.println("Thread " + list[i].getName() + " found.");
         }

         // 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.");
   }
} 

讓我們編譯並執行上述程式，這將產生以下結果：

Starting Thread-0...
Starting Thread-1...
Thread Thread-0 found.
Thread Thread-1 found.
Thread-0 finished executing.
Thread-1 finished executing.

在多個 ThreadGroup 物件中列舉 ThreadObject 物件列表示例

以下示例展示了在多個 ThreadGroup 物件的情況下使用 ThreadGroup enumerate(Thread[] list) 方法。我們建立了一個 ThreadGroup 物件併為其分配了一個名稱。接下來，我們建立了一個子 ThreadGroup 物件。然後，我們使用前面建立的執行緒組物件建立了兩個執行緒。使用 enumerate() 方法，我們將子 ThreadGroup 物件中的所有活動執行緒放入陣列中，然後使用 for 迴圈在陣列上列印它們的名稱。由於子 ThreadGroup 物件只有一個活動執行緒，因此程式將只打印找到的一個執行緒。

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 number of threads put into the array
         Thread[] list = new Thread[cThreadGroup.activeCount()];
         int count = cThreadGroup.enumerate(list);
         for (int i = 0; i < count; i++) {
            System.out.println("Thread " + list[i].getName() + " found.");
         }
            
         // 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.");
   }
} 

讓我們編譯並執行上述程式，這將產生以下結果：

Starting Thread-0...
Starting Thread-1...
Thread Thread-1 found.
Thread-0 finished executing.
Thread-1 finished executing.

在子/孫 ThreadGroup 物件中列舉 ThreadObject 物件列表示例

以下示例展示了在子執行緒組和孫執行緒組物件的情況下使用 ThreadGroup enumerate(Thread[] list) 方法。我們建立了一個 ThreadGroup 物件併為其分配了一個名稱。接下來，我們建立了一個子 ThreadGroup 物件。然後，我們使用前面建立的子執行緒組和孫執行緒組物件建立了兩個執行緒。使用 enumerate() 方法，我們將從祖父 ThreadGroup 物件中獲取所有活動執行緒放入陣列中，然後使用 for 迴圈在陣列上列印它們的名稱。

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 number of threads put into the array
         Thread[] list = new Thread[pThreadGroup.activeCount()];
         int count = pThreadGroup.enumerate(list);
         for (int i = 0; i < count; i++) {
            System.out.println("Thread " + list[i].getName() + " found.");
         }

         // 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.");
   }
} 

讓我們編譯並執行上述程式，這將產生以下結果：

Starting Thread-0...
Starting Thread-1...
Thread Thread-0 found.
Thread Thread-1 found.
Thread-1 finished executing.
Thread-0 finished executing.