What is the Difference Between Constructor and Method

The main difference between constructor and method is that a constructor is a special method in a class that initializes objects of that class while a method is a procedure or a function that executes a set of instructions associated with a class.

Most high-level programming languages support Object Oriented Programming (OOP), which is a methodology that allows the programmers to model real-world scenarios in computing to solve problems. Constructor and method are related to OOP. The constructor is a special kind of method whereas a method is a block of statements.

Key Areas Covered

1. What is Constructor
     – Definition, Functionality
2. What is Method
     – Definition, Functionality
3. What is the Difference Between Constructor and Method
     – Comparison of Key Differences

Key Terms

Class, Constructor, Method, Object, OOP

What is Constructor

A constructor is a special type of method that helps to initialize an object on creation. Also, both class and constructor have the same name. However, a return type is not there in the constructor. Usually, programmers use constructors to give initial values to the instance variables defined in the class.  If the programmer does not define the constructor, the program automatically calls the default constructor. It will initialize all the member variables to zero. But, if the programmer writes his own constructor, then it won’t use the default constructor.

Figure 1: Program with Constructor

In the above Employee class, there is a constructor called Employee. There are two instance variables as id and name. In line 8, there is a constructor, which has the same name as the class name. It initializes the id and name. In the main program, an employee object is created. Finally, the id and name values appears on the console. 

What is Method

A method is a set of statements to perform a certain operation.  Using methods in the program makes it more manageable. It is possible to call the relevant method when required. Also, each method has a name to identify it. And, a method can accept a parameter or not. After performing the task, the method can return a value. Here, if the method returns an integer, the return type is int. But, if the method returns nothing, then the return type is void.

Figure 2: Program with Method

In the above program, an object of MaxFind class is created.  That object calls the maxValue method. It gets two values. The methods check the values and return the maximum value. It will store the maximum value in a variable called max. Finally, the obtained maximum value prints on the console. The maxValue is a method, and it finds the maximum value of these two numbers.

Difference Between Constructor and Method

Definition

A constructor is a special method that usually has the same name as the class, and we can use it to set the values of the members of an object to either default or user-defined values. Whereas, a method is a programmed procedure that is defined as part of a class and included in any object of that class. These definitions give an idea about the fundamental difference between constructor and method.

Return type

To add to this, the constructor has no return type whereas method can return a value or not. Hence, this is another difference between constructor and method.

Default

An important difference between constructor and method is that the program will call the default constructor in case the programmer does not write a constructor. However, there are no default methods.

Name

A constructor has the same name as the class name while a method can have any name other than keywords.

Invocation

One other difference between constructor and method is that the constructors implictly invoke whereas the methods invoke explicitly.

Usage

Furthermore, constructor helps to initialize an object whereas a method helps to exhibit the functionality of an object.

Conclusion

Constructor and method are related to OOP. The main difference between constructor and method is that a constructor is a special method in a class that initializes objects of that class while a method is a procedure or a function that executes a set of instructions associated with a class.

Reference:

1. “Java Methods.” Www.tutorialspoint.com, Available here.
2. “Java Constructors.” Www.tutorialspoint.com, Available here.