Java Constructors

In Java, a constructor is a special type of method that is automatically called when an object of a class is created. Here's an overview of constructors:

Definition:

• A constructor is a method with the same name as the class and no return type (not even void).
• It is used to initialize the state of an object.
• Example:

public class MyClass {
    // Constructor
    public MyClass() {
        // Constructor body
    }
}

Default Constructor:

• If a class does not explicitly define any constructors, a default constructor is automatically provided by the compiler.
• It initializes instance variables to their default values (0, null, false).
• Example:

public class MyClass {
    // Default constructor
    public MyClass() {
        // Constructor body
    }
}

Parameterized Constructor:

• Constructors can accept parameters to initialize instance variables with specified values.
• Example:

public class Person {
    String name;
    int age;

    // Parameterized constructor
    public Person(String n, int a) {
        name = n;
        age = a;
    }
}

Constructor Overloading:

• Like methods, constructors can be overloaded by defining multiple constructors with different parameter lists.
• Example:

public class Student {
    String name;
    int rollNumber;

    // Default constructor
    public Student() {
        // Constructor body
    }

    // Parameterized constructor
    public Student(String n, int r) {
        name = n;
        rollNumber = r;
    }
}

 

Summary

Constructors play a crucial role in initializing objects and setting their initial state. Understanding how to define and use constructors is essential for creating objects and initializing their properties in Java.