Java Java.lang.Object.wait()用法及代碼示例

描述

這個java.lang.Object.wait()導致當前線程等待，直到另一個線程為此對象調用 notify() 方法或 notifyAll() 方法。換句話說，這個方法的行為就像它隻是執行調用 wait(0) 一樣。

當前線程必須擁有此對象的監視器。線程釋放此監視器的所有權並等待，直到另一個線程通過調用 notify 方法或 notifyAll 方法通知在此對象監視器上等待的線程喚醒。然後線程等待直到它可以擁有監視器的 re-obtain 所有權並恢複執行。

此方法隻能由作為此對象監視器的所有者的線程調用。有關線程可以成為監視器所有者的方式的描述，請參閱通知方法。

聲明

以下是聲明java.lang.Object.wait()方法

public final void wait()

參數

NA

返回值

此方法不返回值。

異常

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

• InterruptedException- 如果另一個線程中斷了當前線程。拋出此異常時清除當前線程的中斷狀態。

示例

下麵的例子展示了 lang.Object.wait() 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!