java-design-patterns/monostate/README.md

---
layout: pattern
title: MonoState
folder: monostate
permalink: /patterns/monostate/
categories: Creational
language: en
tags:
 - Instantiation
---

## Also known as
Borg

## Intent
Enforces a behaviour like sharing the same state amongst all instances.

## Class diagram
![alt text](./etc/monostate.png "MonoState")

## Applicability
Use the Monostate pattern when

* The same state must be shared across all instances of a class.
* Typically this pattern might be used everywhere a Singleton might be used. Singleton usage however is not transparent, Monostate usage is.
* Monostate has one major advantage over singleton. The subclasses might decorate the shared state as they wish and hence can provide dynamically different behaviour than the base class.

## Typical Use Case

* The logging class
* Managing a connection to a database
* File manager

## Real world examples

Yet to see this.
Monostate pattern #85 2015-10-04 03:06:11 +05:30			`---`
			`layout: pattern`
			`title: MonoState`
			`folder: monostate`
			`permalink: /patterns/monostate/`
			`categories: Creational`
fix: Fixed pages showing up in wrong language (#1752) * Fix languages * Missed change for version number * Add language field for presentation * Revert change in README for double buffer Co-authored-by: Jackie Nim <=> 2021-05-19 10:49:05 -06:00			`language: en`
Categorize and tag all patterns #213 2015-12-28 15:52:44 +02:00			`tags:`
https://github.com/iluwatar/java-design-patterns-web/issues/8 Update pattern categories and tags 2019-12-13 21:09:28 +02:00			`- Instantiation`
Monostate pattern #85 2015-10-04 03:06:11 +05:30			`---`

#459 added known aliast for monostate pattern 2016-07-26 20:33:43 +02:00			`## Also known as`
			`Borg`

Use headings instead of bold text in index.md #238 2016-01-03 21:14:30 +01:00			`## Intent`
			`Enforces a behaviour like sharing the same state amongst all instances.`
Monostate pattern #85 2015-10-04 03:06:11 +05:30
#1113 Link uml-reverse-mapper created class diagrams to readme, where needed 2019-12-07 20:01:13 +02:00			`## Class diagram`
Monostate pattern #85 2015-10-04 03:06:11 +05:30			`![alt text](./etc/monostate.png "MonoState")`

Use headings instead of bold text in index.md #238 2016-01-03 21:14:30 +01:00			`## Applicability`
			`Use the Monostate pattern when`
Monostate pattern #85 2015-10-04 03:06:11 +05:30
			`* The same state must be shared across all instances of a class.`
Made changes according to feedback issue #258 2015-10-09 23:20:58 +05:30			`* Typically this pattern might be used everywhere a Singleton might be used. Singleton usage however is not transparent, Monostate usage is.`
Monostate pattern #85 2015-10-04 03:06:11 +05:30			`* Monostate has one major advantage over singleton. The subclasses might decorate the shared state as they wish and hence can provide dynamically different behaviour than the base class.`

Use headings instead of bold text in index.md #238 2016-01-03 21:14:30 +01:00			`## Typical Use Case`
Monostate pattern #85 2015-10-04 03:06:11 +05:30
https://github.com/iluwatar/java-design-patterns-web/issues/8 Update pattern categories and tags 2019-12-13 21:09:28 +02:00			`* The logging class`
			`* Managing a connection to a database`
			`* File manager`
Monostate pattern #85 2015-10-04 03:06:11 +05:30
Use headings instead of bold text in index.md #238 2016-01-03 21:14:30 +01:00			`## Real world examples`
Monostate pattern #85 2015-10-04 03:06:11 +05:30
			`Yet to see this.`