what is generics & why we need generics ?

What is generic and why we need generics ?


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Generics are introduced in Java 5 to provide the type checking at compile time. If you use generics, you need not to perform the type casting explicitly. Java compiler applies strong type checking if you use generics in your code and shows errors if the code violates the type safety. Thus removing the risk of ClassCastException.

Therefore, To write the type safety code and to remove the risk of ClassCastException at run time, we need generics.

n a nutshell, generics enable types (classes and interfaces) to be parameters when defining classes, interfaces and methods. Much like the more familiar formal parameters used in method declarations, type parameters provide a way for you to re-use the same code with different inputs. The difference is that the inputs to formal parameters are values, while the inputs to type parameters are types.

Code that uses generics has many benefits over non-generic code:

Stronger type checks at compile time.
A Java compiler applies strong type checking to generic code and issues errors if the code violates type safety. Fixing compile-time errors is easier than fixing runtime errors, which can be difficult to find.

In the simplest definition, generic programming is a style of computer programming in which algorithms are written in terms of types to-be-specified-later that are then instantiated when needed for specific types provided as parameters. This approach, pioneered by ML in 1973, permits writing common functions or types that differ only in the set of types on which they operate when used, thus reducing duplication. Such software entities are known as generics in Ada, Delphi, Eiffel, Java, C#, F#, Objective-C, Swift, and Visual Basic .NET; parametric polymorphism in ML, Scala, Haskell (the Haskell community also uses the term "generic" for a related but somewhat different concept) and Julia; templates in C++ and D; and parameterized types in the influential 1994 book Design Patterns. The authors of Design Patterns note that this technique, especially when combined with delegation, is very powerful but also quote the following