Java.util.Observable.hasChanged() Method


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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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