Java - ThreadGroup enumerate(ThreadGroup[] list, boolean recurse) 方法

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描述

Java ThreadGroup enumerate(ThreadGroup[] list, boolean recurse) 方法將此執行緒組中的每個活動子組的引用複製到指定的陣列中。如果recurse標誌為 true，則還包括所有子組的活動子組的引用，依此類推。

宣告

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

public int enumerate(ThreadGroup[] list,boolean recurse)

引數

  • list − 這是要放置執行緒組列表的陣列。

  • recurse − 此標誌指示是否要遞迴列舉所有包含的執行緒組。

返回值

此方法返回放入陣列中的執行緒組數。

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(ThreadGroup[] list, boolean recurse) 方法的情況。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 threadgroup 物件建立了兩個執行緒。使用 enumerate() 方法，我們將所有子執行緒組放入陣列中，然後使用 for 迴圈在陣列上列印它們的名稱。由於沒有子組，因此計數將為零。

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 thread groups put into the array
         ThreadGroup[] grpList = new ThreadGroup[threadGroup.activeGroupCount()];
         int count = threadGroup.enumerate(grpList,true);
         for (int i = 0; i < count; i++) {
            System.out.println("Thread " + grpList[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.");
   }
}

輸出

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-1 finished executing.
Thread-0 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(ThreadGroup[] list, boolean recurse) 方法的情況。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 threadgroup 物件建立了兩個執行緒。使用 enumerate() 方法，我們將所有子執行緒組從父 ThreadGroup 物件放入陣列中，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 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 thread groups put into the array
         ThreadGroup[] grpList = new ThreadGroup[pThreadGroup.activeGroupCount()];
         int count = pThreadGroup.enumerate(grpList,true);
         for (int i = 0; i < count; i++) {
            System.out.println("ThreadGroup " + grpList[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.");
   }
}

輸出

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...
ThreadGroup Child ThreadGroup found.
Thread-0 finished executing.
Thread-1 finished executing.

在子/孫子物件中列舉 ThreadObject 物件列表示例

以下示例展示了在子 ThreadGroup 物件和孫子 ThreadGroup 物件的情況下使用 ThreadGroup enumerate(ThreadGroup[] list, boolean recurse) 方法的情況。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子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從祖父母 ThreadGroup 物件放入陣列中，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 thread groups put into the array
         ThreadGroup[] grpList = new ThreadGroup[pThreadGroup.activeGroupCount()];
         int count = pThreadGroup.enumerate(grpList,true);
         for (int i = 0; i < count; i++) {
            System.out.println("ThreadGroup " + grpList[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.");
   }
}

輸出

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...
ThreadGroup Child ThreadGroup found.
ThreadGroup GrandChild ThreadGroup found.
Thread-0 finished executing.
Thread-1 finished executing.
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