---
title: What is Java Constructor?
description: "***What is Java Constructor?*** A Java constructor is a special method used to initialize objects when they are created. It is called automatically when an object of a class is instantiated. Constructors have the same name as the class and…"
url: "https://vinothqaacademy.com/docs/what-is-java-constructor/"
updated: "2025-10-05"
category: Java
tags:
  - Java
---

# What is Java Constructor?

***What is Java Constructor?***

A Java constructor is a special method used to initialize objects when they are created. It is called automatically when an object of a class is instantiated. Constructors have the same name as the class and do not have a return type, not even *void.*

### **Key Characteristics of Constructors:**

1. **Name:** A constructor must have the same name as the class in which it is defined.

2. **No Return Type:** Constructors do not have a return type, not even void.

3. **Automatic Invocation:** Constructors are automatically called when an object is created.

4. **Overloading:** Java allows constructor overloading, meaning a class can have more than one constructor with different parameter lists.

### **Types of Constructors:**

1. **Default Constructor:**
   - **Definition:** A default constructor is a no-argument constructor provided by Java if no other constructors are defined. It initializes object fields with default values.

***Example:***

```javascript

                class Person {

    String name;

    int age;

    // Default constructor

    Person() {

        name = "Unknown";

        age = 0;

    }

}

public class Main {

    public static void main(String[] args) {

        Person p = new Person();

        System.out.println("Name: " + p.name);

        System.out.println("Age: " + p.age);  

    }

}

Output:
Name: Unknown
Age: 0
```

1. **Parameterized Constructor:**
   - **Definition:** A parameterized constructor allows initializing object fields with specific values provided during object creation.

***Example:***

```javascript

                class Person {

    String name;

    int age;

    // Parameterized constructor

    Person(String name, int age) {

        this.name = name;

        this.age = age;

    }

}

public class Main {

    public static void main(String[] args) {

        Person p = new Person("Alice", 30);

        System.out.println("Name: " + p.name);

        System.out.println("Age: " + p.age);  

    }

}

Output:
Name: Alice
Age: 30
```

**Constructor Overloading:**

Java allows multiple constructors in a class, each with different parameter lists. This is known as constructor overloading.

***Example:***

```javascript

                class Person {

    String name;

    int age;

    // Default constructor

    Person() {

        name = "Unknown";

        age = 0;

    }

    // Parameterized constructor

    Person(String name, int age) {

        this.name = name;

        this.age = age;

    }

    // Another parameterized constructor with different parameters

    Person(String name) {

        this.name = name;

        this.age = 0;

    }

}

public class Main {

    public static void main(String[] args) {

        Person p1 = new Person();

        Person p2 = new Person("Bob", 25);

        Person p3 = new Person("Charlie");

        System.out.println("p1 Name: " + p1.name + ", Age: " + p1.age);

        System.out.println("p2 Name: " + p2.name + ", Age: " + p2.age);

        System.out.println("p3 Name: " + p3.name + ", Age: " + p3.age);

    }

}

Output:
p1 Name: Unknown, Age: 0
p2 Name: Bob, Age: 25
p3 Name: Charlie, Age: 0
```

**Summary**

Constructors are essential for initializing new objects in Java. They can be default or parameterized, and Java supports constructor overloading, allowing multiple constructors with different parameters to be defined in a single class.