---
title: "How are Observer and Observable used?"  
description: "How are Observer and Observable used?"  
author: "Sumit Kesarwani"  
published: 2014-08-26  
updated: 2020-09-15  
canonical: https://www.mindstick.com/interview/2016/how-are-observer-and-observable-used  
category: "java"  
tags: ["java"]  
reading_time: 1 minute  

---

# How are Observer and Observable used?

Objects that subclass the Observable class maintain a list of observers. When an Observable object is updated it invokes the update() method of each of its observers to notify the observers that it has changed state. The Observer interface is implemented by objects that observe Observable objects.

## Answers

### Answer by Sumit Kesarwani

Objects that subclass the Observable class maintain a list of observers. When an Observable object is updated it invokes the update() method of each of its observers to notify the observers that it has changed state. The Observer interface is implemented by objects that observe Observable objects.


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Original Source: https://www.mindstick.com/interview/2016/how-are-observer-and-observable-used

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