1) Constructor is a member method of a class used to initialize values to data members.
A method is used to do some computations by an object such as input, calculate and display.
2) The name of the constructor is the name of the class.
A method’s name is different from the class.
3) Constructor has no return type even void.
A member method is always with a return type.
4) Constructor is invoked at the time of object creation.
A member method is invoked by a method call.

The new operator is used to create objects and arrays at runtime; it allocate memory for objects and arrays.
E.g.:
object creation: Rectangle rect1 = new Rectangle();
array creation: int a[] = new int[10];

* The constructor with default values is a default constructor. When we define a constructor with default values such as 0 or null then this is a default constructor.
* And if we define a class without constructor then the compiler provides a constructer at the time of object creation with default values such as 0 or null; so this also is considered as default constructor.
E.g.:
public Student( )
{
roll=0;
name= “”;
mark=0.0;
}

A constructor is used to create objects by initializing proper values to the data members. It executes at the time of object creation.
E.g.: Recatangle r = new Rectangle();

The class keyword and class name.

An object named staff belonging to class Employee is created.

The this keyword is used to store the address of current object in order to avoid ambiguity when local variable names and instance variable names are same and class ariable names and instance variable names are same. The this keyword represents current object.

A class which is defined as data type to create objects and composed of various member variables and member methods is a composite data type. E.g.:
public class Student
{
public int roll;
public String name;
public double mark;
}

(i) student
(ii) There is no class variable, but instance variables are x and y
(iii) a,b
(iv) member method/void. access().

1) The name of the constructor is name of the class and it is used to initialize values to variable.
2) It has no return type even void and it executes at the time of object creation.

Several constructors for a class with different initialization by different data types or different number of arguments is known as constructor overloading. Note that the constructor names are same because name of the constructor is name of the class. So different objects can initialize different values to their data members. E.g.:
class Shapes
{
float s;
double l,b;
Shapes(float x)
{
s=x;
}
Shapes(double x, double y)
{
l=x;
b=y;
}
public static void main()
{
Shapes sq=new Shapes(10.0f);
Shapes rect=new Shapes(8.5,4.3);
}
}

class A
{
int a;
A() //default constructor
{
a=0;
}
A(int x) //parameterized constructor
{
a=x;
}
public static void main()
{
A ob1=new A();
A ob2=new A(0);
}
}

(j) (i) String args[], int n
(ii) static int x
(iii) int a
(iv) int y

The name of the constructor is same as class name and it is used to initialize legal values to instance variables..
The name of the method is different from the class and it is used to do some functions like input, process and output.

(i) void
(ii) this

A constructor is a member method with the same name of class and it is used to initialize legal values to the data members. A constructor is invoked at the time of object creation.

(ii) arr[i]
(iii) obj
(vi) str;

Parameterized Constructor and Non-Parameterized constructor.

this

(c) Parameterized constructor is a constructor that has parameter and intializes values to the data members when object is created.

Primitive data types are fundamental data types defined by language developers. It can store only one value at a time. E.g.: int.
Composite data types are data types based on primitive data type as well as reference data type. Users also can define composite data types. It can contain multiple values. E.g.: a class named Student which consists int roll; String name; etc.

Constructor is member method with the name of class and it is used to initialize values to data members and it has no return type.
Name of a Function is different of class and it is used for computations like input, process and output and it has a return type.

(i) A constructor is member function with its class name and it is used to create objects by initialising values to data memebrs.
(ii) A constructor has no return type and it is invoked at the time of object creation.

Several constructors having different initializations even though the names are same that are differentiable by number of arguments or types of arguments is known as constructor overloading. E.g.:
class A
{
int a;
double b;
A()
{ a=3; }
A(double x)
{ b=x; }
}