Design Patterns are very popular among software developers. A design pattern is a well-described solution to

common software problem.

Some of benefits of using design patterns are :

* Design patterns are already defined and provides industry standard approach to solve reccuring problem,

so it saves time if we senibly use the design pattern .

* Using design pattern promotes reusability that leads to more robust and hightly maintenable code.

* Since design patterns are already defined, it makes out code easy to understand and debug. It lead to faster developement and new members of team understand it easily.

__Java Design Patterns__ are divived into tree parts : *Creational*, *Structural* and *Behavioral*.

Creational design pattens provide solution to instatiate an object in the best possible way for specific situations.

The basic form of object creation could result in design problems or add unwanted complexity to the design. Creational design patterns solve this problem by __controlling the object creation__ by different ways.

There are five creational design patterns that we will discuss :

1 .Singleton Pattern

2. Factory Pattern

3. Abstract Factory Pattern

4. Builder Pattern

4. Prototype Pattern

Pattern Singleton: > One Class, one Instance.

Singleton is one of the Gangs of Four Design patterns and comes in the Creational Design Pattern category.

Singleton pattern restricts the instantiation of a class and ensures that only one instance of the class exists in the java virtual machine. The singleton class must provide a global access point to get the instance of the class. Singleton pattern is used for logging, driver objects, caching and thread pool. Singleton design pattern is also used in other design patterns like __Abstract Factory__, __Builder__, __Prototype__, __Facade__ etc. Singleton design pattern is used in core java classes also, for example __java.lang.Runtime__ , __java.awt.Desktop__.

To implement Singleton pattern, there are really many approaches but all of them have following common concepts:

* A private constructor to avoid instantiation of the class,

* A private static variable from the same class that's the only instance of the class.

* public static method that returns the instance of the class, this is the global access point for the outer world to

get the instance of the class.

We'll implement the thread safe one here. Classes are in the package `com.singleton`;