In software engineering, a design pattern is a general repeatable solution to a commonly occurring problem in software design. A design pattern is not a finished design that can be transformed directly into code. It is a description or template for how to solve a problem that can be used in many different situations.Java Design Patterns are divided into three categories: creational, structural, and behavioral design patterns. For a very long time there was a serious problem in software engineering: you hire a newcomer to a project and no matter how well they know the programming language, it takes them months to get up to speed with how things are done in your project before they can be productive. In hardware engineering, they solved this problem a very long time ago. They have a common terminology called ‘schematic diagrams’. You hire a hardware engineer, give them the schematics of your hardware project in the morning, allow them to study it, and by evening before it is time to call it a day they can pick up the soldering gun and become productive.