Difference between Constructor and Method in Java

Constructors vs. Methods

Let us take an example to illustrate the difference between Constructor and Method in detail: 

We have a Person class that has two instance variables, name and age, which are declared as private to ensure encapsulation. 

As soon as we create the object of the Person class, the constructor gets invoked. On the other hand, the method needs to be invoked using the object. 

Code in Java

• java

java

/* Java program to illustrate the difference
   between Constructor and Method
*/
public class Person {
    private String name;
    private int age;


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


    // method
    public void sayHello() {
        System.out.println("Hello, my name is " + name + " and I am " + age + " years old.");
    }
    
    // main method
    public static void main(String[] args) {
        Person p = new Person("Ninja", 20);
        p.sayHello();
    }
}

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Run Code

Output

Hello, my name is Ninja and I am 20 years old.

This code demonstrates the difference between constructors and methods, where the constructor is used to initialize the state of an object, and the method is used to perform operations on the object.

Difference between Constructor and Method

Below are some main differences between the constructor and method: 

Read more about, Difference Between Rank and Dense Rank

Example of Constructor vs Method

Let us discuss an example of a constructor vs method with output:

• java

java

// This code prints the message "I love coding ninjas"
// and changes the name of the person to "Dhruv"

class Person {
    private String name;

    public Person() {
        this.name = "Dhruv";
        System.out.println("Creating a new person named Dhruv");
    }

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

    public String getName() {
        return this.name;
    }

    public void sayHello() {
        System.out.println("Hello, my name is " + this.name);
    }
}

public class Main {
    public static void main(String[] args) {
        Person person = new Person();
        System.out.println(person.getName()); // Dhruv
        person.setName("Dhruv");
        System.out.println(person.getName()); // Dhruv
        person.sayHello(); // Hello, my name is Dhruv
    }
}

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Run Code

The Person class contains a constructor that initializes the name property to the value "Dhruv". It also has methods to set and get the value of the name property and a method to print a greeting message.

The Main class creates a new Person object and prints the name of the object. After that, it changes the name of the object and prints the name again. Finally, it calls the sayHello() method to print a greeting message.
 

Output:

Dhruv
Dhruv
Hello, my name is Dhruv

Frequently Asked Questions

Can a method have the same name as the constructor?

Yes, a method can have the same name as the constructor, but it should have a different attribute list; this is called method overloading.

What is the difference between the constructor and the main method?

A constructor initializes an object when it is created, while the main method is the entry point of a Java application, used to run the program.

What is the difference between a constructor and an object in Java?

A constructor is a special method used to initialize an object, while an object is an instance of a class, representing a specific realization of the class blueprint.

What is the difference between a constructor and a method signature?

A constructor has no return type and shares the class name, while a method signature includes the method's name and parameter list, optionally with a return type.

What is the difference between constructor and method overloading in Java?

A constructor initializes new objects, while method overloading allows multiple methods with the same name but different parameters within a class, enabling different implementations.

Conclusion

To summarize the discussion, we have discussed the difference between Constructor and method in detail. We have also discussed the types of constructors along with various examples. 

After reading about the key difference between constructor and method, if you feel like going in-depth and knowing more about each of them, Don't worry, refer to our recommended articles :

Constructors and Destructors

Default Constructor in Java

Virtual Constructor and Destructor to learn more about constructors and methods.

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