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Java.util.Observable.notifyObservers() Method
Description
The java.util.Observable.notifyObservers(Object arg) method notify all of its observers if this object has changed and then call the clearChanged method to indicate that this object has no longer changed.
Declaration
Following is the declaration for java.util.Observable.notifyObservers() method
public void notifyObservers(Object arg)
Parameters
arg − Any object.
Return Value
NA
Exception
NA
Example
The following example shows the usage of java.util.Observable.notifyObservers(Object) method.
package com.tutorialspoint; import java.util.Observable; import java.util.Observer; class ObservedObject extends Observable { private String watchedValue; public ObservedObject(String value) { watchedValue = value; } public void setValue(String value) { // if value has changed notify observers if(!watchedValue.equals(value)) { System.out.println("Value changed to new value: "+value); watchedValue = value; // mark as value changed setChanged(); // trigger notification with arguments notifyObservers(value); } } } public class ObservableDemo implements Observer { public String name; public ObservableDemo(String name) { this.name = name; } public static void main(String[] args) { // create watched and watcher objects ObservedObject watched = new ObservedObject("Original Value"); // watcher object listens to object change ObservableDemo watcher = new ObservableDemo("Watcher"); // add observer to the watched object watched.addObserver(watcher); // trigger value change watched.setValue("New Value"); } public void update(Observable obj, Object arg) { System.out.println(name+" called with Arguments: "+arg); } }
Let us compile and run the above program, this will produce the following result −
Value changed to new value: New Value Watcher called with Arguments: New Value
java_util_observable.htm
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