Java Generics Tutorial

Generics in Java enable classes, interfaces, and methods to operate on types specified by the client at the time of use. This feature brings stronger type checks at compile time, eliminates the need for type casting, and allows for more generalized and reusable code. Let’s delve into a comprehensive yet straightforward tutorial on Java generics with examples.

Introduction to Generics

Generics were introduced to Java in JDK 5 to extend the language’s expressiveness while ensuring type safety and reducing runtime errors.

Basic Syntax:

  • Generic classes: class ClassName<T> { /*...*/ }
  • Generic methods: public <T> ReturnType methodName(T param) { /*...*/ }

Example 1: A Generic Class

Let’s start with a simple generic class that can store any type of object.

Example 2: A Generic Method

Now, let’s look at a generic method that can work with any type of array and finds the middle element.

Example 3: Bounded Type Parameters

You can limit the types that can be used in generic methods and classes. This is known as bounded type parameters.

Example 4: Generic Interfaces

Interfaces can also be generic. Here’s how you can define and implement a generic interface.

Example 5: Wildcards

Wildcards (?) allow for more flexibility when dealing with type parameters, particularly when you’re not sure about the type of objects you’ll need to work with.


Generics in Java provide a way to write code that is more type-safe, reusable, and readable. By allowing types to be parameters when defining classes, interfaces, and methods, generics enable you to create flexible and generalized code that can operate on various data types. Through the use of generics, Java developers can achieve strong type checking at compile time and avoid the pitfalls of type casting and runtime errors.

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