What is the Difference Between Default and Parameterized Constructor? with Proper Definition and Brief Explanation

The default constructor is a type of constructor that is automatically called when the programmer has not defined any constructors in the program. In contrast, the parameterized constructor is a type of constructor defined by the programmer by passing parameters to give initial values ​​to instance variables in the class. That is the main difference between default and parameterized constructor.

Most high-level programming languages ​​support object-oriented programming (OOP). In OOP, everything is a class, which helps build objects. These objects communicate with each other in the program. The constructor is a concept in OOP. It is a special method that allows you to initialize an object on creation. The constructor can be default or parameterized.

Key Areas Covered

1. What is the default constructor?
     – Definition, Functionality
2. What is the parameterized constructor?
     – Definition, Functionality
3. What is the difference between default and parameterized constructor?
     – Comparison of key differences

Key terms

Constructor, default constructor, OOP, parameterized constructor

What is the default constructor?

The constructor is called when an object is created. It also allocates memory for that object. Also, it helps to give initial values ​​to instance variables in the class. If the programmer does not define a constructor, the program calls the default constructor automatically. Initializes all member variables to zero or null.

                                             Figure 1: Program with default constructor

In the above program, there is a class of students. It has two instance variables like id and name. The programmer did not define any constructors. Also, there is a student object in the main method. Finally, the id and name are printed to the console. Since no constructor was defined by the programmer, the program calls the default constructor. Initialize the ID to 0 and the name to null.

What is parameterized constructor?

The parameterized constructor is a constructor that accepts parameters. There may be one or more parameters. When there is a parameterized constructor, the program does not call the default constructor. Also, the programmer can declare the parameters in parentheses after the constructor name.

                                       Figure 2: Program with parameterized constructor

Above is a class called Calculus. It has two instance variables called num1 and num2. On line 7, there is a parameterized constructor. It takes two arguments x and y and assigns those values ​​to the instance variables num1 and num2.

Also, there is a method called sum. It will return the sum of those two numbers. There is a calculation object in the main method. The sum method is called using obj1. Finally, the results are printed to the console.

Difference Between Default and Parameterized Constructor

Definition

The default constructor is a constructor that is automatically generated by the compiler in the absence of any programmer-defined constructors. Conversely, parameterized constructor is a constructor that the programmer creates with one or more parameters to initialize the instance variables of a class. Thus, this explains the main difference between default and parameterized constructor.

Number of Parameters

Parameters are an important difference between default and parameterized constructor. The default constructor has no parameters, while the parameterized constructor has one or more parameters.

Calling Method

If the programmer omits to write a constructor, the program automatically calls the default constructor. On the other hand, the programmer must write his own constructor when writing a parameterized constructor.

Conclusion

The default constructor is a type of constructor that is automatically called when no constructor has been defined by the programmer in the program. In contrast, the parameterized constructor is a type of constructor defined by the programmer by passing parameters to give initial values ​​to instance variables in the class. That is the main difference between default and parameterized constructor.

Reference:

1. “Java Builder – Javatpoint.” Www.javatpoint.com , Available here.

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