Software Engineers and Developers choose a design pattern to start a project using particular design pattern to start a project. These are helpful to solve the Specific coding and design problems in the real time projects.
Design Patterns also called as Reusable Object Oriented Software.
These are the different types of design patterns used in real time world to develop projects.

* Creational patterns

o Abstract Factory Design Pattern
o Builder Design Pattern
o Factory Method Design Pattern
o Object Pool Design Pattern
o Prototype Design Pattern
o Singleton Design Pattern

* Structural patterns

o Adapter Design Pattern
o Bridge Design Pattern
o Composite Design Pattern
o Decorator Design Pattern
o Facade Design Pattern
o Flyweight Design Pattern
o Private Class Data
o Proxy Design Pattern

* Behavioral patterns

o Chain of Responsibility
o Command Design Pattern
o Interpreter Design Pattern
o Iterator Design Pattern
o Mediator Design Pattern
o Memento Design Pattern
o Null Object Design Pattern
o Observer Design Pattern
o State Design Pattern
o Strategy Design Pattern
o Template Method Design Pattern
o Visitor Design Pattern

1.First u open notepad and write program like.

  

Then

2.Go in D Drive and create new file name as myjava

3.saveas  D drive in myjava folder name as same name of class name  “ HelloWorld.java”  

suppose we save the program in D: \myjava 

Then

4.open command prompt like

And then write

And press Enter key

Then  write cd <file name>

Then press Enter key

Then set path

Press Enter

Then set classpath

Then press Enter

And compile the java program like

And press Enter

Then run the program like

Press Enter key and enjoy the first program in java