Understanding List of Generic Class Objects in Java
Table of Contents
- Introduction
- Overview of Generics in Java
- Understanding the Code
- Example Code Explanation
- Key Takeaways and Conclusion
1. Introduction
Generics in Java are a powerful feature that allows developers to define classes, interfaces, and methods with type parameters. This enables code reusability and type safety, making it easier to work with collections and custom data structures. In this article, we will explore the concept of creating a list of generic class objects in Java, supported by a practical code example.
This guide is aimed at beginner to intermediate developers with basic knowledge of Java, who wish to deepen their understanding of generics and how they can be used in real-world applications.
2. Overview of Generics in Java
Generics were introduced in Java 5 to allow for type-safe operations, especially when dealing with collections. They eliminate the need for typecasting and reduce runtime errors by providing compile-time type checking.
In the context of this article, we will focus on creating a List that holds generic objects, allowing for greater flexibility and reusability.
Pros:
- Type safety: Generics enforce compile-time checks, ensuring that the code handles specific types correctly.
- Code reusability: A single generic class or method can work with different data types without the need for duplication.
Cons:
- Complexity: Generics can be hard to grasp initially, especially for beginners.
- No primitive types: Generics only work with reference types, not primitive types (e.g., int, char).
Comparison Table: Generics vs Non-generics
| Feature | With Generics | Without Generics |
|---|---|---|
| Type safety | Enforced at compile-time | Runtime errors possible |
| Code reuse | High | Low |
| Typecasting | Not required | Required |
3. Understanding the Code
Below is the Java code that demonstrates how to create a List of generic class objects. The class Data is a generic class that takes a type parameter <T>, allowing it to hold different types of objects:
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 |
package org.studyeasy; import java.util.LinkedList; import java.util.List; class Data<T> { private T object; public Data(T object) { this.object = object; } @Override public String toString() { return object.toString(); } } public class Main { public static void main(String[] args) { List<Data<String>> elements = new LinkedList<>(); elements.add(new Data<>("Chaand")); elements.add(new Data<>("StudyEasy")); for (Data<String> data : elements) { System.out.println(data); } } } |
4. Example Code Explanation
The Data<T> class:
This class is a generic class with a type parameter <T>. It can hold an object of any type specified when creating an instance. The toString() method is overridden to return the string representation of the object stored.
Creating the List of generic objects:
In the main() method, we create a List that holds objects of type Data<String>. We populate this list using the add() method and pass in objects of type String.
Iteration and printing:
The for loop iterates over each Data<String> object in the list and prints it. Since the toString() method is overridden in the Data class, it prints the string representation of the object.
Output:
|
1 2 |
Chaand StudyEasy |
5. Key Takeaways and Conclusion
Generics are a powerful feature in Java that enhances type safety and code reusability. By using generic classes and collections like List, we can write flexible and reusable code that works with different data types without compromising type safety.
In this article, we have covered:
- How to create a generic class in Java.
- Using a
Listto store objects of a generic class. - How generics improve code safety and flexibility.
By applying these concepts, developers can write cleaner and more robust Java applications.