Java Java.lang.Object.notifyAll()用法及代碼示例

描述

這個java.lang.Object.notifyAll()喚醒在此對象監視器上等待的所有線程。線程通過調用等待方法之一在對象的監視器上等待。

被喚醒的線程將無法繼續，直到當前線程放棄對該對象的鎖定。被喚醒的線程將以通常的方式與可能正在積極競爭以同步此對象的任何其他線程進行競爭；例如，被喚醒的線程在成為下一個鎖定該對象的線程時不享有可靠的特權或劣勢。

此方法隻能由作為此對象監視器的所有者的線程調用。

聲明

以下是聲明java.lang.Object.notifyAll()方法

public final void notifyAll()

參數

NA

返回值

此方法不返回值。

異常

IllegalMonitorStateException- 如果當前線程不是該對象監視器的所有者。

示例

下麵的例子展示了 lang.Object.notifyAll() 方法的用法。

package com.tutorialspoint;

import java.util.Collections;
import java.util.LinkedList;
import java.util.List;

public class ObjectDemo extends Object {

   private List synchedList;

   public ObjectDemo() {
      // create a new synchronized list to be used
      synchedList = Collections.synchronizedList(new LinkedList());
   }

   // method used to remove an element from the list
   public String removeElement() throws InterruptedException {
      synchronized (synchedList) {

         // while the list is empty, wait
         while (synchedList.isEmpty()) {
            System.out.println("List is empty...");
            synchedList.wait();
            System.out.println("Waiting...");
         }
         String element = (String) synchedList.remove(0);

         return element;
      }
   }

   // method to add an element in the list
   public void addElement(String element) {
      System.out.println("Opening...");
      synchronized (synchedList) {

         // add an element and notify all that an element exists
         synchedList.add(element);
         System.out.println("New Element:'" + element + "'");

         synchedList.notifyAll();
         System.out.println("notifyAll called!");
      }
      System.out.println("Closing...");
   }

   public static void main(String[] args) {
      final ObjectDemo demo = new ObjectDemo();

      Runnable runA = new Runnable() {

         public void run() {
            try {
               String item = demo.removeElement();
               System.out.println("" + item);
            } catch (InterruptedException ix) {
               System.out.println("Interrupted Exception!");
            } catch (Exception x) {
               System.out.println("Exception thrown.");
            }
         }
      };

      Runnable runB = new Runnable() {

         // run adds an element in the list and starts the loop
         public void run() {
            demo.addElement("Hello!");
         }
      };

      try {
         Thread threadA1 = new Thread(runA, "A");
         threadA1.start();

         Thread.sleep(500);

         Thread threadA2 = new Thread(runA, "B");
         threadA2.start();

         Thread.sleep(500);

         Thread threadB = new Thread(runB, "C");
         threadB.start();

         Thread.sleep(1000);

         threadA1.interrupt();
         threadA2.interrupt();
      } catch (InterruptedException x) {
      }
   }
}

讓我們編譯並運行上麵的程序，這將產生以下結果——

List is empty...
List is empty...
Opening...
New Element:'Hello!'
notifyAll called!
Closing...
Waiting...
Hello!
Waiting...
List is empty...
Interrupted Exception!