This document discusses constructors in Java. It defines a constructor as a special method used to initialize objects. Constructors can be compiler-defined, non-parameterized, or parameterized. Constructors are called implicitly when an object is created and can only be called once per object. They differ from methods in that methods can be called multiple times and allow return types while constructors do not. The document also covers constructor overloading and using the this() call to call another constructor.

1. Submitted to :-
MR. R.S.Rawat Sir
(H.O.D. of it department)
Submitted by:-
Puneet tiwari
B.e. viith sem
enroll no.:-0601it131034

2.  contents
• What is Constructor.
• Properties of constructor.
• Difference B/w constructors and methods.
• Types of constructors.
• Constructor overloading.
• This();--constructor call

3.  What is Constructor
• The constructor is a special method used to
initializing object.
• A block of code which has to be executed on
creation of object is defined inside constructor.
• It is used to initialize non static variables of a class.

4. Properties of constructor
• Constructor name is same name as class name.
• Constructor does not have return value not even
void.
• Constructors only allows access modifiers.
• It is called implicitly at time of creating object.
• It is called only once on one object.

5.  Difference between constructors
and methods
• Method is called any number of times on the object.
• Constructor is called only once on object.
• Method is called explicitly.
• Constructor is called implicitly.
• Methods allow access and non access modifiers.
• It Allows only access modifiers.
• Method name can be any name.
• Constructor name must be same as class name.
• Methods are inherited.
• These are not inherited.

6.  Types of constructors
Constructors
User defined
constructors
Non parameterized
constructors
Parameterized
constructors
Compiler defined
constructors
Default

7. 1. Compiler defined constructor
• If there is no constructors within a class compiler
provide default constructor without any
parameter this is called as default constructor.
• Default constructor access modifier is same as
class.

8.  Example
Abc.java Abc.class
Class Abc
{
int x;
int y;
}
Class Abc
{
int x;
int y;
Abc()
{
super();
}
}

9. 2. User defined constructor
• Constructor defined by programmer is called the user
defined constructor.
I. Non parameterized constructor– A constructor
written in a class without any parameter is called as
non parameterized constructor.
This constructor does not receive any value.

10.  Example
class A
{
A()
{
System.out.println(“Inside Constructor ”);
}
void A()
{
System.out.println(“Inside Method”);
}
}
Class Main
{
public static void main(String [ ] args)
{
A obj1=new A();
obj1.A();
}
}
Output –
Inside Constructor
Inside Method

11. II. Parameterized constructor- parameterized constructor is
user defined constructor.
• This constructor receive values at the time of creating objects
• This constructor allow two types of parameters.
i. Primitive types.
ii. Reference types.
• If constructor having primitive type it receive value.
• If constructor having reference type it receive address of object.

12.  Example
class cons
{
private int no;
private String name;
cons(int no,String name)
{
this.no=no;
this.name=name;
}
void display()
{
System.out.println(no);
System.out.println(name);
}
}
class Main
{
public static void main(String [ ] args)
{
cons obj1=new cons(101,"Puneet");
obj1.display();
}
output-
101
puneet

13. Constructor overloading
• Defining more than one constructor within a class with same
name is called as constructor overloading.
• The constructors must be change in at least one criteria.
I. Number of parameters.
II. Types of parameters.
III. Order of parameters.
• Constructor is overloaded to extend functionality of existing
constructor.

14.  Example
class Abc
{
Abc()
{
System.out.println("Non parameterized constructor");
}
Abc(int a,String s)
{
System.out.println(a);
System.out.println(s);
}
}
class Main
{
public static void main(String [ ] args)
{
Abc obj1=new Abc();
Abc obj2=new Abc(601,"Igec Sagar");
}
output-
Non parameterized constructor
601
Igec Sagar

15. Constructor call-using this();
• One constructor call another constructor of same
class using “this()” constructor call.
• It allows code reusability.
• It is used inside the constructor but not inside the
method.

16.  Example
class Abc
{
Abc()
{
System.out.println("Non parameterized constructor");
}
Abc(int x)
{
this();
System.out.println("parameterized constructor");
}
}
class Main
{
public static void main(String [ ] args)
{
Abc obj1=new Abc(10);
}
}
Output--
Non parameterized constructor
Parameterized constructor

17. Java is like a sea if you are too much thirsty then only you can able to learn it as whole--.