---
layout: pattern
title: Thread Local Storage
folder: tls
permalink: /patterns/tls/
pumlid: 
categories: Concurrency
tags:
 - Java
 - Difficulty-Intermediate
---

## Intent
Securing variables global to a thread against being spoiled by other threads. That is needed if you use class variables or static variables in your Callable object or Runnable object that are not read-only.

![alt text](./etc/tls.png "Thread Local Storage")

## Applicability
Use the Thread Local Storage in any of the following situations

* when you use class variables in your Callable / Runnable object that are not read-only and you use the same Callable instance in more than one thread running in parallel.
* when you use static variables in your Callable / Runnable object that are not read-only and more than one instances of the Callable / Runnable may run in parallel threads.