User Defined Data Type in Java

There are two types of data types in Java: primitive data types and reference data types. Primitive data types include int, char, boolean, etc while reference data types include objects and arrays. However, it is also possible to create our own data types in Java through the use of user defined data types.

There are two main types of user defined data types in Java:

• Classes and
• Interfaces.

A class is a template that can be used to create objects, while an interface is a set of related methods with empty bodies.

User defined data type example

Following is an example of creating a user defined data type in Java:

// Define a class called Person
public class Person {
    // Instance variables (data)
    String name;
    int age;

    // Constructor
    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

    // Methods
    public void introduce() {
        System.out.println("Hi, my name is " + name + " and I'm " + age + " years old.");
    }
}

In the example above, we define a class called Person. The Person class has two instance variables: name of type String and age of type int. We also define a constructor that takes the name and age as parameters and assigns them to the respective instance variables.

The Person class also has a method called introduce(), which prints out a simple introduction message using the name and age instance variables.

To use this user-defined data type, you can create objects of the Person class:

// Create a Person object
Person person1 = new Person("Virat Kohli", 31);

// Access the instance variables
System.out.println(person1.name); // Output: Virat Kohli
System.out.println(person1.age);  // Output: 31

// Call the introduce() method
person1.introduce(); // Output: Hi, my name is Virat Kohli and I'm 31 years old.

In the example above, we create a Person object named person1 using the new keyword and passing the constructor arguments. We can then access the instance variables (name and age) and call the introduce() method on the person1 object.

By defining your own classes, you can create complex data structures, encapsulate data and behavior together, and create reusable code components in your Java programs.

Frequently Asked Questions