java.lang.Object.wait()方法範例

java.lang.Object.wait() 導致當前執行緒等待，直到其他執行緒呼叫notify()方法或notifyAll()方法，此物件。換言之，此方法的行為就好像它簡單地執行呼叫wait(0)。

當前執行緒必須擁有該物件的監視器。該監視器並等待另一個執行緒的執行緒釋放所有權通知的執行緒在等待此物件的監視器上無論是通過呼叫notify方法或notifyAll方法喚醒。該執行緒要等到重新獲得對監視器的所有權後才能繼續執行。

這個方法只能由一個執行緒是此物件監視器的所有者被呼叫。看到其中一個執行緒能夠成為監視器所有者的notify方法。

宣告

以下是java.lang.Object.wait()方法的宣告

public final void wait()

引數

返回值

這個方法沒有返回值。

異常

IllegalMonitorStateException -- 如果當前執行緒不是物件監視器的擁有者。
InterruptedException -- 如果另一個執行緒中斷了當前執行緒。當這種異常被丟擲當前執行緒的中斷狀態被清除。

例子

下面的例子顯示lang.Object.wait()方法的使用。

package com.yiibai;

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) {
      }
   }
}

讓我們來編譯和執行上面的程式，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!