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Java.lang.Object.notifyAll() Method
Description
The java.lang.Object.notifyAll() wakes up all threads that are waiting on this object's monitor. A thread waits on an object's monitor by calling one of the wait methods.
The awakened threads will not be able to proceed until the current thread relinquishes the lock on this object. The awakened threads will compete in the usual manner with any other threads that might be actively competing to synchronize on this object; for example, the awakened threads enjoy no reliable privilege or disadvantage in being the next thread to lock this object.
This method should only be called by a thread that is the owner of this object's monitor.
Declaration
Following is the declaration for java.lang.Object.notifyAll() method
public final void notifyAll()
Parameters
NA
Return Value
This method does not return a value.
Exception
IllegalMonitorStateException − if the current thread is not the owner of this object's monitor.
Example
The following example shows the usage of lang.Object.notifyAll() method.
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) { } } }
Let us compile and run the above program, this will produce the following result −
List is empty... List is empty... Opening... New Element:'Hello!' notifyAll called! Closing... Waiting... Hello! Waiting... List is empty... Interrupted Exception!