Constructor is a special method used to initialize an value for instance variable when the object created.
When we created and object, constructor will automatically run.
Constructor name will be the class name
Syntax:
Class Name
{
int id;
Name(int id) //constructor
}
Why Constructor?
It is used to Initialize the value immediately.
No chance for creating incomplete object.
Types of Constructor:
- Default constructor
- No parameter
- Provided by java if we don't provide any constructor.
- Parameterized constructor:
- Has parameter.
- Used to pass value while creating object.
Example:
Test(int a)
{
System.out.println(100);
}
Example for constructor:
Scenario: In the student register name and roll no must be entered initially.
package moduleFour;
public class College {
int rollno;
String name;
College(int rollno,String name)
{
this.rollno = rollno;
this.name = name;
}
public static void main(String[] args) {
College student1 = new College(2001,"Kavin");
College student2 = new College(2002,"Nethra");
System.out.println(student1.rollno);
System.out.println(student2.name);;
}
}
Output:
2002
Nethra
_Constructor Overloading: _
Constructor overloading is creating object in different ways with multiple constructor with different parameter.
(i.e) having more than one constructor in same class with different parameter
Why?
To create object in different ways.
To provide default or custom values for object.
Example for Constructor Overloading:
package moduleFour;
public class College2 {
int rollno;
String name;
int age;
College2(int rollno,String name,int age)
{
this.rollno = rollno;
this.name = name;
this.age = age;
}
College2(int rollno,String name)
{
this.rollno = rollno;
this.name = name;
}
public static void main(String[] args) {
College2 student1 = new College2(2001,"Kavin",18);
College2 student2 = new College2(2002,"Nethra");
System.out.println(student1.rollno); //2001
System.out.println(student1.age); //18
System.out.println(student2.name); // Nethra
}
}
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