1. Constructors are special member functions that initialize objects and allocate memory. They have the same name as the class and do not have a return type. 2. There are three types of constructors: default, simple, and parameterized. The default constructor is provided by Java if no constructor is defined, and has no arguments. 3. Methods are functions that belong to a class and perform tasks. There are simple, parameterized, and returning methods. Simple methods perform tasks without arguments, parameterized methods take arguments, and returning methods return a value.

1. Constructor and Method in

2. Constructor
Constructor is a special member function whose main
operation is to allocate the required resources such as
memory and initializes the object of its class.
Property of Constructor
It has same name as class name.
It has no return type.
It is automatically requested for help when the object
is created.
It is declared in the public section.
It cannot be overridden.
Its default argument is zero.
Sub class constructor can call super class constructor.

3. Types of constructor
Default constructor
Simple constructor
Parameterized constructor
Default constructor
There is no constructor in a class, java provides default
constructor.
Its argument is zero.

4. Simple constructor
class student
{
int rollno;
String name;
// this is constructor of student class
student()
{
rollno=11;
name=”HARSH”;
}
}

5. class demo
{
public static void main(String args[])
{
student s1 = new student();
System.out.println(“Roll number is = ”+s1.rollno);
System.out.println(“Name is = ”+s1.name);
}
}
Output
Roll number is = 11
Name = HARSH

6. Parameterized constructor
class student
{
int rollno;
String name;
student(int rno, String nm)
{
rollno=rno;
name=nm;
}
}

7. class demo
{
public static void main(String args[])
{
student s1 = new student(11,"HARSH");
System.out.println("Roll number is = "+s1.rollno);
System.out.println("Name is = "+s1.name);
}
}
Output
Roll number is = 11
Name is = HARSH

8. Method
Method is small part of the program that has some meaning and it has
some task for the program.
Methods are used to access class data.
Types of Method
Simple Method
Parameterized Method
Method Returning Method

9. Simple method
class box
{
double width;
double height;
double depth;
// parameterized constructor of box
box(double w, double h, double d)
{
width=w;
height=h;
depth=d;
}
// simple method to calculate volume
void calvol()
{
System.out.println("Volume of a box is = "+(width*height*depth));
}
}

10. class demo
{
public static void main(String args[])
{
box b1 = new box(10,10,10);
// method is called
b1.calvol();
}
}
Output
Volume of box is = 1000

11. Parameterized Method
class box
{
double width;
double height;
double depth;
// Parameterized Method to set dimention
void setdim(double w, double h, double d)
{
width=w;
height=h;
depth=d;
}
// simple method to calculate volume
void calvol()
{
System.out.println("Volume of a box is = "+(width*height*depth));
}
}

12. class demo
{
public static void main(String args[])
{
box b1 = new box();
b1.setdim(10,10,10);
b1.calvol();
}
}
Output
Volume of box is = 1000

13. Method returning value
class box
{
double width;
double height;
double depth;
// parameterized constructor of box
box(double w, double h, double d)
{
width=w;
height=h;
depth=d;
}
// method returning a value to main()
double calvol()
{
return(width*height*depth);
}
}

14. class demo
{
public static void main(String args[])
{
box b1 = new box(10,10,10);
double vol = b1.calvol();
System.out.println("Volume of box is = "+vol);
}
}
Output
Volume of box is = 1000

15. Prepared by
Harsh Jani
jani99harsh@gmail.com
[CCET]