Inheritance

Inheritance is a mechanism in which one class (say child class or derived class) derives the properties i.e. methods and fields of another class(say a parent or base class) including itself.

Use of Inheritance:

Code Reusability: Inheritance is mostly used to increase the reusability(using the same piece of code oftentimes).
Efficient Program Structure: Simplifies code maintenance and modification.
Supports Runtime Polymorphism: Helps in method overriding and achieving dynamic method dispatch.

Syntax:

class child_class-name extends parent_class-name
{
     // your code
}

Example:

package quipohouse;

class Parent{
int a=10;

void parentMethod() {
System.out.println("Inside Parent Class");    
  }
}
class Child extends Parent{
int b=10;
void childMethod() {
System.out.println("Inside Child Class");
}
public static void main(String[] args) {

Child c=new Child();
c.childMethod();                                      //child method is invoked
c.parentMethod();                                     //parent method is invoked
System.out.println("field of child class-"+c.b);      //child class field
System.out.println("field of parent class-"+c.a);     //parent class field
   }
}

Output:

Inside Child Class
Inside Parent Class
field of child class-10
field of parent class-10

Explanation:

The Child class inherits the properties of the Parent class.
The object of Child class (c) is able to access both child and parent methods & fields.
This shows how inheritance allows reusability of code.