A constructor is a method used to initialize the object. It is automatically called when a class is instantiated.

 Types of Constructor

1. Default Constructor:

• Constructors declared without parameters are called Default constructors
• It provides default values (i.e.- 0, NULL) to objects.

Syntax:

Class_name ( ) 
{  
    // body
}

 Example:

package quipohouse;
class Message {
	Message() {
		System.out.println("QUIPO HOUSE");
	}

	public static void main(String[] args) {
		Message obj = new Message();
	}
}

Output:

QUIPO HOUSE

2 . Parameterized Constructor:

• Constructors declared with parameters are called Parameterized constructors.
• It provides different values to objects.

Syntax:

Class_name(para1,para2 )
{  
     // body
}

Example:

package quipohouse;
public class Identifier {
	String msg, msg1;
	Identifier(String msg, String msg1) {
		// This keyword refer current class object
		this.msg = msg;
		this.msg1 = msg1;
	}

	void message() {
		System.out.println(msg + "" + msg1);
	}

	public static void main(String[] args) {
		Identifier obj = new Identifier(" Message ", " msg ");
		obj.message();
	}
}

Output:

Message  msg 

class Employee {
    String name;
    int age;

    // Parameterized Constructor
    Employee(String name, int age) {
        this.name = name;
        this.age = age;
    }

    // Copy Constructor
    Employee(Employee e) {
        this.name = e.name;
        this.age = e.age;
    }

    void display() {
        System.out.println("Name: " + name + ", Age: " + age);
    }

    public static void main(String[] args) {
        Employee e1 = new Employee("John", 25);
        Employee e2 = new Employee(e1); // Copy Constructor

        e1.display();
        e2.display();
    }
}

Name: John, Age: 25
Name: John, Age: 25

class Student {
    String name;
    int age;

    // Default Constructor calling Parameterized Constructor
    Student() {
        this("Unknown", 0);
    }

    Student(String name, int age) {
        this.name = name;
        this.age = age;
    }

    void display() {
        System.out.println("Name: " + name + ", Age: " + age);
    }

    public static void main(String[] args) {
        Student s1 = new Student();
        Student s2 = new Student("Alice", 22);
        s1.display();
        s2.display();
    }
}

Name: Unknown, Age: 0
Name: Alice, Age: 22