Java Java.lang.Object.wait()用法及代码示例

描述

这个java.lang.Object.wait()导致当前线程等待，直到另一个线程为此对象调用 notify() 方法或 notifyAll() 方法。换句话说，这个方法的行为就像它只是执行调用 wait(0) 一样。

当前线程必须拥有此对象的监视器。线程释放此监视器的所有权并等待，直到另一个线程通过调用 notify 方法或 notifyAll 方法通知在此对象监视器上等待的线程唤醒。然后线程等待直到它可以拥有监视器的 re-obtain 所有权并恢复执行。

此方法只能由作为此对象监视器的所有者的线程调用。有关线程可以成为监视器所有者的方式的描述，请参阅通知方法。

声明

以下是声明java.lang.Object.wait()方法

public final void wait()

参数

NA

返回值

此方法不返回值。

异常

• IllegalMonitorStateException- 如果当前线程不是对象监视器的所有者。

• InterruptedException- 如果另一个线程中断了当前线程。抛出此异常时清除当前线程的中断状态。

示例

下面的例子展示了 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) {
      }
   }
}

让我们编译并运行上面的程序，这将产生以下结果 -

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