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inheritance

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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