Classes in Java
Class : Whatever we can see in this world
all the things are a object.
And all the objects are categorized in a special group. That group is
termed as a class.
All the objects are direct interacted with its class that mean almost all
the properties of the object should be matched with it's own class. Object
is the feature of a class which is used for the working on the particular
properties of the class or its group. We can understand about the class
and object like this : we are all the body are different - different
objects of the human being class. That means all the properties of a
proper person relates to the human being. Class has many other features
like creation and implementation of the object, Inheritance etc.
In this Program you will see how to use the
class, object and it's methods. This program uses the several values of
several defined variables for getting the Area and Perimeter of the Square
and Rectangle by calling the different functions from the different
classes through the several objects created for the several class. In this
program there are two classes has been used except the main class in which
the main function is declared. First class is square which is used for
getting the Area and Perimeter of the square and another class is
rectangle which is used for getting the Area and Perimeter of the
Rectangle. All the functions in the square and rectangle class are calling
with different - different arguments two times for getting the Area and
Perimeter of square and rectangle for two different sides. This program
gives us the Area and Perimeter for the different sided Square and
Rectangle separately. Full running code is given with the example :
Here is the code of the program :
class square{
int sqarea(int side){
int area = side * side;
return(area);
}
int sqpari(int side){
int pari = 4 * side;
return(pari);
}
}
class rectangle{
int rectarea(int length,int breadth){
int area = length * breadth;
return(area);
}
int rectpari(int length,int breadth){
int pari = 2*(length + breadth);
return(pari);
}
}
public class ObjectClass{
public static void main(String args[]){
int sarea1,sarea2,pari1,pari2;
int rectarea1,rectarea2,rectpari1,rectpari2;
square sq = new square();
rectangle rect = new rectangle();
int a=20;
System.out.println("Side of first square = " + a);
sarea1 = sq.sqarea(a);
pari1 = sq.sqpari(a);
System.out.println("Area of first square = " + sarea1);
System.out.println("Parimeter of first square = " + pari1);
a = 30;
System.out.println("Side of second square = " + a);
sarea2 = sq.sqarea(a);
pari2 = sq.sqpari(a);
System.out.println("Area of second square = " + sarea2);
System.out.println("Parimeter of second square = " + pari2);
int x = 10, y = 20;
System.out.println("Length of first Rectangle = " + x);
System.out.println("Breadth of first Rectangle = " + y);
rectarea1 = rect.rectarea(x,y);
rectpari1 = rect.rectpari(x,y);
System.out.println("Area of first Rectangle = " + rectarea1);
System.out.println("Parimeter of first Rectangle = " + rectpari1);
x = 15;
y = 25;
System.out.println("Length of second Rectangle = " + x);
System.out.println("Breadth of second Rectangle = " + y);
rectarea2 = rect.rectarea(x,y);
rectpari2 = rect.rectpari(x,y);
System.out.println("Area of second Rectangle = " + rectarea2);
System.out.println("Parimeter of first Rectangle = " + rectpari2);
}
} |
Descriptions of the program:
Object : Objects are the basic run time
entity or in other words object is a instance of a class . An object is a
software bundle of variables and related methods of the special class. In
the above example the sq is the object of square class and rect is the
object of the rectangle class. In real-world objects share two
characteristics: They have all state and behavior. For example, The
squares have state such as : sides and behaviors such as its areas and
perimeters. Rectangles have state such as: length, breadth and behavior
such as its areas and perimeters. A object implements its behavior with
methods of it's classes. A method is a function (subroutine) associated
with an object.
Syntax for the Object :
class_name object_name = new class_name();
Output of the program :
|
C:\chandan>javac ObjectClass.java
C:\chandan>java ObjectClass
Side of first square = 20
Area of first square = 400
Parimeter of first square = 80
Side of second square = 30
Area of second square = 900
Parimeter of second square = 120
Length of first Rectangle = 10
Breadth of first Rectangle = 20
Area of first Rectangle = 200
Parimeter of first Rectangle = 60
Length of second Rectangle = 15
Breadth of second Rectangle = 25
Area of second Rectangle = 375
Parimeter of first Rectangle = 80
|
Constructor: Every
class has at least one it's own constructort.
Constructor creates a instance for the class. Constructor initiates
(initialize) something related to the class's methods. Constructor is the
method which name is same to the class. But there are many difference
between the method (function) and the Constructor.
In this example we will see that how to to
implement the constructor feature in a class. This program is using two
classes. First class is another and
second is the main class which name is Construct.
In the Construct class
two objects (a and
b) are created
by using the overloaded another Constructor
by passing different arguments and calculated the are of the different
rectangle by passing different values for the another
constructor.
Here is the code of the program :
class another{
int x,y;
another(int a, int b){
x = a;
y = b;
}
another(){
}
int area(){
int ar = x*y;
return(ar);
}
}
public class Construct{
public static void main(String[] args)
{
another b = new another();
b.x = 2;
b.y = 3;
System.out.println("Area of rectangle : " + b.area());
System.out.println("Value of y in another class : " + b.y);
another a = new another(1,1);
System.out.println("Area of rectangle : " + a.area());
System.out.println("Value of x in another class : " + a.x);
}
} |
Output of the program :
C:\chandan>javac
Construct.java
C:\chandan>java Construct
Area of rectangle : 6
Value of x in another class : 3
Area of rectangle : 1
Value of x in another class : 1 |
Constructor Overloading:
Here, you will learn more about Constructor
and how constructors are overloaded in Java. This section provides you a
brief introduction about the Constructor that are overloaded in the
given program with complete code absolutely in running state i.e. provided
for best illustration about the constructor overloading in Java.
Constructors are used to assign initial values to
instance variables of the class. A default constructor with no arguments
will be called automatically by the Java Virtual Machine (JVM).
Constructor is always called by new operator. Constructor
are declared just like as we declare methods, except that the constructor
don't have any return type. Constructor can be overloaded provided they
should have different arguments because JVM differentiates constructors on
the basis of arguments passed in the constructor.
Whenever we assign the name of the method same as
class name. Remember this method should not have any return type. This is
called as constructor overloading.
We have made one program on a constructor
overloading, after going through it the concept of constructor overloading
will get more clear. In the example below we have made three overloaded
constructors each having different arguments types so that the JVM
can differentiates between the various constructors.
The code of the program is given below:
public class ConstructorOverloading{
public static void main(String args[]){
Rectangle rectangle1=new Rectangle(2,4);
int areaInFirstConstructor=rectangle1.first();
System.out.println(" The area of a rectangle in
first constructor is : " + areaInFirstConstructor);
Rectangle rectangle2=new Rectangle(5);
int areaInSecondConstructor=rectangle2.second();
System.out.println(" The area of a rectangle in
first constructor is : " + areaInSecondConstructor);
Rectangle rectangle3=new Rectangle(2.0f);
float areaInThirdConstructor=rectangle3.third();
System.out.println(" The area of a rectangle in first
constructor is : " + areaInThirdConstructor);
Rectangle rectangle4=new Rectangle(3.0f,2.0f);
float areaInFourthConstructor=rectangle4.fourth();
System.out.println(" The area of a rectangle in first
constructor is : " + areaInFourthConstructor);
}
}
class Rectangle{
int l, b;
float p, q;
public Rectangle(int x, int y){
l = x;
b = y;
}
public int first(){
return(l * b);
}
public Rectangle(int x){
l = x;
b = x;
}
public int second(){
return(l * b);
}
public Rectangle(float x){
p = x;
q = x;
}
public float third(){
return(p * q);
}
public Rectangle(float x, float y){
p = x;
q = y;
}
public float fourth(){
return(p * q);
}
} |
Output of the program is given below:
C:\java>java
ConstructorOverloading
The area of a rectangle in first constructor is : 8
The area of a rectangle in first constructor is : 25
The area of a rectangle in first constructor is : 4.0
The area of a rectangle in first constructor is : 6. |
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