What is the use of @data class in Java

Java is still one of the most popular and efficient programming languages in the constantly changing field.

Java's power is its ability to adapt in dealing with modern programming paradigms without sacrificing its security and simplicity. The @data class annotation is one of the features that was added to Java most recently. 

The use and importance of Java's @data class will be discussed in this article, along with how it improves code readability and speeds development.

Understanding the Basics of @data Class

We need to first look at the core idea behind the @data class to fully appreciate its usefulness. 

Classes are the fundamental units of object-oriented programming in Java. Because they encapsulate activity and data, developers may write modular, reusable programs. 

However, traditional Java classes often require a considerable amount of boilerplate code for basic functionalities such as getters, setters, equals(), hashCode(), and toString() methods. The @data class annotation is useful in this situation.

The @data annotation is a powerful feature provided by the Project Lombok library in Java. The @Data annotation saves developers time and effort by automatically generating equals(), hashCode(), getters, setters, and toString() functions. 

When developing classes that contain basic data structures, such as POJOs (Plain Old Java Objects), this annotation is quite helpful.

Use Cases and Examples

Let's look at a practical example where a class is needed to represent products in an e-commerce application. 

Traditionally, writing getters, setters, equals(), hashCode(), and toString() methods are required to create such a class. However, the code can be made much simpler by utilizing the @data class annotation:

Code without @data annotation

public class Student {

	private int rollno;
	private String name;
	private String position;
	
	public Student(int rollno, String name, String position) {
		super();
		this.rollno = rollno;
		this.name = name;
		this.position = position;
	}

	public int getRollno() {
		return rollno;
	}

	public void setRollno(int rollno) {
		this.rollno = rollno;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getPosition() {
		return position;
	}

	public void setPosition(String position) {
		this.position = position;
	}

	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result + ((name == null) ? 0 : name.hashCode());
		result = prime * result + ((position == null) ? 0 : position.hashCode());
		result = prime * result + rollno;
		return result;
	}

	@Override
	public String toString() {
		return "Student [rollno=" + rollno + ", name=" + name + ", position=" + position + "]";
	}
		
}

Code with @data annotation

This code defines a Product class with three fields: name, price, and category. The @Data annotation automatically generates the following methods for this class:

1) A constructor that takes name, price, and category as parameters.

2) Getters for name, price, and category.

3) Setters for name, price, and category.

4) An equals() method that compares two Person objects based on their name, price, and category fields.

5) A hashCode() method that returns a hash code based on the name, price, and category fields.

6) A toString() method that returns a string representation of the Product object.

@Data
public class Product {
    private final String name;
    private final double price;
    private final String category;
}

Second Example,

This class represents a user with a name and an age. The @Data annotation tells Lombok to generate all the necessary boilerplate code for us, including getters, setters, a toString() method, an equals() method, and a hashCode() method.

@Data
public class User {
  private String name;
  private int age;
}

Benefits of Using @data Class

Automatic Generation of Boilerplate Code:

Java automatically creates necessary methods like equals(), hashCode(), and toString() with the @data class annotation, saving developers from having to write tedious and repetitive code. This automation lowers the possibility of making mistakes while increasing efficiency.

Immutable Data Structures:

Immutable objects are those derived from @data classes whose states cannot be changed after they are instantiated. Because immutable objects are by nature thread-safe, their immutability ensures data integrity and makes concurrent programming easier.

Enhanced Readability and Conciseness:

@data classes provide code that is clearer and shorter by doing away with the requirement for explicit getter and setter methods. The codebase is easier to comprehend and manage thanks to this increased readability, especially for developers who are new to the project.

Effective Pattern Matching:

Java's pattern-matching features are smoothly integrated with @data classes, enabling programmers to create clear, expressive code for managing complex data structures. Pattern matching improves the readability of the code and makes conditional tests easier.

Time Savings:

You can save significant development time by focusing more on the main logic of your application with the automatic production of common methods.

Reduced Errors: 

The @data annotation minimizes human error and possible execution errors by minimizing the amount of handwritten code.

Maintenance and Consistency: 

To maintain consistency across the codebase, when a class's fields are changed, the generated methods that go along with it are also immediately updated.