Inheritance In Java Classes

Inheritance:

Inheritance is a mechanism in Java that allows you to extend a class with another class. In Java, Inheritance “is a” relationship i.e., teacher is a employee see below code example of inheritance.

Create a new class as an extension of another class to make it more powerful. That is, the derived class inherits the public methods and public data of the base class. Java only allows a class to have one immediate base class means no multiple inheritance i.e., single class inheritance.

For example:  

public class Employee {

       private int id;

       private String name;

             

         //parameterized constructor

         public Employee(int id, String name){

             this.id = id;

             this.name = name;

         }

         //default constructor

         public Employee(){

                id = 10;

                name = "not set";

         }

        

         public void display(){

             System.out.println("Employee id:" + id + " name:" + name);

         }

}

public class Teacher extends Employee {//here Teacher extending(inheriting) the Employee class

   private String qualification;

   //default constructor

   public Teacher () {

        //implicit call to superclass default constructor          

        qualification = "";     

   }

   //parameterized constructor

   public Teacher(int id, String name, String qual){

       super(id,name); //call to superclass(Employee) constructor must be in first line       

       qualification = qual;

   }

  

  

   public void displayResult(){

  

         super.display(); //call to superclass(Employee) display method

         System.out.println("Qualifications :" + qualification);

   }

}

public class Test {

       public static void main(String[] args) {

             

         System.out.println("Making Object Of Employee Class");

         Employee employee = new Employee(10, "Rehan Ali");  

        

  employee.display(); //call to Employee class display method

            

         System.out.println("Making Object Of Teacher Class");

         Teacher teacher = new Teacher (12, "Ali Haider", "Mcs");

          

         teacher.displayResult(); //call to Teacher class displayResult method

     }

}

Output:

Making Object Of Employee Class

Employee Id:10 name:Rehan Ali

Making Object Of Teacher Class

Employee Id:12 name:Ali Haider

Qualifications : Mcs