Constructor In Java: A Simple But Complete Guide
Constructor In Java: A Simple But Complete Guide
#python #java-programming #Constructor #constructor-in-java
BY TEJAS
A constructor is a very important feature in Java. Also, a constructor is an important topic in object-oriented programming.
A constructor is a member function of any class whose name is the same as the name of the class. In simple language, if we learn, we make an object just like we make an object of a class, but its name is the same as the name of the class. The constructor does not have any return type. The constructor is used to set the initial values of functions.
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Java has two types of constructors.
1. NULL Constructor
2. Parameterized Constructor
import java.lang.*;
class student {
String name;
int marks1, marks2, marks3, regno;
// NULL constructor
student() {
name = "raju";
regno = 12345;
marks1 = 56;
marks2 = 47;
marks3 = 78;
}
// parameterized constructor
student(String n, int r, int m1, int m2, int m3) {
name = n;
regno = r;
marks1 = m1;
marks2 = m2;
marks3 = m3;
}
void display() {
System.out.println(name + "\t" + regno + "\t" + marks1 + "\t" + marks2 + "\t" + marks3);
}
}
class Constructor {
public static void main(String arg[]) {
student s1 = new student();
student s2 = new student("john", 34266, 58, 96, 84);
s1.display();
s2.display();
}
}
This is the Output Of Program
Program Output
Looking at the above program, you may have got some idea of what a constructor is?. What is a NULL constructor & what is a Parameterized constructor?
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1. NULL Constructor
In NULL Constructor we set the values directly.
In the NULL constructor, you do not define any parameter in the function. Outside of Function, we
define all datatypes and keywords. And then in the function, we assign values to those
keywords.
Your concept will be completely clear by watching the program given below.
import java.lang.*;
class student {
String name;
int marks1, marks2, marks3, regno;
// null constructor
student() {
name = "raju";
regno = 12345;
marks1 = 56;
marks2 = 47;
marks3 = 78;
}
void display() {
System.out.println(name + "\t" + regno + "\t" + marks1 + "\t" + marks2 + "\t" + marks3);
}
}
class StudentDemo {
public static void main(String arg[]) {
student s1 = new student();
s1.display();
}
}
Null Constructor Output
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2. Parameterized constructor
In a parameterized constructor we set the values first and then pass those values to the
constructor.
In a parameterized constructor we can define any parameters in the function. In this, we can define
datatype and keywords in the parenthesis of a function. And then like NULL Constructor we assign
values to those keywords.
You will get a crystal clear idea by watching the program given below.
import java.lang.*;
class student {
String name;
int marks1, marks2, marks3, regno;
// parameterized constructor
student(String n, int r, int m1, int m2, int m3) {
name = n;
regno = r;
marks1 = m1;
marks2 = m2;
marks3 = m3;
}
void display() {
System.out.println(name + "\t" + regno + "\t" + marks1 + "\t" + marks2 + "\t" + marks3);
}
}
class StudentDemo {
public static void main(String arg[]) {
student s2 = new student("john", 34266, 58, 96, 84);
s2.display();
}
}
Parameterized Constructor Output
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Conclusion
As we saw in the above article, what are the concepts of constructor in java? There are two types of
NULL Constructor and Parameterized Constructor.
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