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Java.util.Observable.hasChanged() Method
Description
The java.util.Observable.hasChanged() method returns if this object has changed.
Declaration
Following is the declaration for java.util.Observable.hasChanged() method
public boolean hasChanged()
Parameters
NA
Return Value
This method returns true if object has changed (by a recent call to setChanged method), otherwise it returns false.
Exception
NA
Example
The following example shows the usage of java.util.Observable.hasChanged() 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)) { watchedValue = value; // mark as value changed setChanged(); } } } 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 System.out.println("setValue method called..."); watched.setValue("New Value"); // check if value has changed if(watched.hasChanged()) System.out.println("Value changed"); else System.out.println("Value not changed"); } public void update(Observable obj, Object arg) { System.out.println("Update called"); } }
Let us compile and run the above program, this will produce the following result −
setValue method called... Value changed
java_util_observable.htm
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