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Introduction to Java


In this lesson, you will learn about one of the most powerful features in Java, which allows you to write flexible and reusable code. Generics were introduced in Java 5; since then, they have become a crucial part of Java development.

What are Generics

First of all, let's define what Generics are. Generics allow you to write a class or method that can work with objects of different types. This means you can create a single class or method that can handle objects of different classes without having to write separate code for each type. This results in more concise, flexible, and maintainable code.

For example, consider a simple scenario where you need to create a class to store a list of items. Without Generics, you would have to create a separate class for each type of item you want to store, such as Strings, Integers, or any other type of object. With Generics, you can write a single class that can store any object.

Example of Generics

Here is an example of how you can use Generics to create a class for storing a list of items:


In this example, the class ListExample is parameterized with a type T, which can be any object. When you create an instance of this class, you can specify the type you want to use. For example, look at the code below.


Similarly, you can create an instance of ListExample for any object you want to store. The key to using Generics effectively is understanding the concept of type parameters and type arguments. A type parameter is a placeholder for a type that will be specified later, such as T in the ListExample class. A type argument is an actual type that is passed when an instance of the class is created, such as a String in the example above. Generics also provide type safety, which means you can catch type-related errors at compile-time instead of runtime. This makes your code more robust and less prone to errors. Another important aspect of Generics is Bounds. Bounds allow you to restrict the types of objects used with a class or method. For example, you might want to write a method that only accepts objects that implement a specific interface. To do this, you can specify a bound on the type parameter:


In this example, the type parameter T is bounded by the Comparable interface. Only objects that implement the Comparable interface can be used with the sort method.


Generics is a powerful and essential tool for writing flexible and reusable code in Java. They allow you to write code handling objects of different types, providing type safety and reducing the need for writing separate code for each type. Using type parameters and Bounds, you can write code that is easy to understand and maintain and can be adapted to handle different types of objects as your needs change.

1. What is the purpose of Generics in Java?
2. What is a type parameter in Java Generics?


What is the purpose of Generics in Java?

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What is a type parameter in Java Generics?

Select the correct answer

Section 5.

Chapter 3