INHERITANCE:-Inheritance
is the process of code re-usability, using this property software or
applications can develop in less time or can develop rapidly. Inheritance increases
the readability of code and decrease redundancy or repetition of code or
reduces size of code.
Use of previously developed code in future any number of times is
called inheritance. Through inheritance variables and methods of class can
inherited.
Types of Inheritance:-
1) Single
or Single level inheritance
2) Multilevel
inheritance
3) Hierarchical
inheritance
Java does not support to multiple inheritance.
Single or single level inheritance:-In a single inheritance a class is
inherited by a single class. In a single or single level inheritance a sub
class having only one super class directly or indirectly.
Syntax: - class Subclass
extends Superclass
Here extends is a keyword used for inheritance in java language.
Example1:-Sum of two numbers without using inheritance.
class Student
{
int a,b;
void sum()
{
a=10;
b=20;
System.out.println("sum= "+(a+b));
}
public static void main(String[]args)
{
Student s=new Student();
s.sum();
}
}
Output:-
C:\JAVATECH>javac Student.java
C:\JAVATECH>java Student
sum= 30
Here Student class have a code to do sum of two numbers, if
another class like Test want to perform same operation (sum of two numbers)
than Test class minimum required two variables for holding values and a
function to perform addition of variables.
Example2:-Student.java
class Test
{
int a,b;
void add()
{
a=100;
b=200;
System.out.println("sum of = "+(a+b));
}
}
class Student
{
int a,b;
void sum()
{
a=10;
b=20;
System.out.println("sum= "+(a+b));
}
public static void main(String[]args)
{
Student s=new Student();
s.sum();
Test t=new Test();
t.add();
}
}
Output:-
C:\JAVATECH>javac Student.java
C:\JAVATECH>java Student
sum= 30
sum of = 300
In the above example both the classes perform same operation and
sum method of Student class, add method of Test class having same code or
duplicate code.
Example3:- Sum of two numbers using inheritance.
class Test extends Student
{
}
class Student
{
int a,b;
void sum()
{
a=10;
b=20;
System.out.println("sum= "+(a+b));
}
public static void main(String[]args)
{
Student s=new Student();
s.sum();
Test t=new Test();
t.sum();
}
}
Output:-
C:\JAVATECH>javac Student.java
C:\JAVATECH>java Student
sum= 30
sum= 30
Example4:- Sum of two numbers using inheritance.
class Student
{
int a,b;
void sum()
{
a=10;
b=20;
System.out.println("sum= "+(a+b));
}
public static void main(String[]args)
{
Student s=new Student();
s.sum();
Test t=new Test();
t.sum();
}
}
class Test extends Student
{
}
Output:-
C:\JAVATECH>javac Student.java
C:\JAVATECH>java Student
sum= 30
sum= 30
Example5:- Sum of two numbers using inheritance
(Test1.java).
class Student
{
int a,b;
void sum()
{
a=10;
b=20;
System.out.println("sum= "+(a+b));
}
}
class Test extends Student
{
}
class Test1
{
public static void main(String[]args)
{
Test t=new Test();
t.sum();
}
}
Output:-
C:\JAVATECH>javac Test1.java
C:\JAVATECH>java Test1
sum= 30
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