Wednesday, October 28, 2015

Inheritance with Java GUI

Prepare a input form which will take 2 input for range of values. After getting input from the user, find sum of all primes from the given range using a button named Generate-Sum. After getting the sum check whether the sum is even or not.  All the process will be done by a class followed by Inheritance in Java. You have to display the output in a label at Form.

Inheritance in Java Programming


Why use inheritance in java

  • For Code Reusability.

Syntax of Java Inheritance

  1. class Subclass-name extends Superclass-name  
  2. {  
  3.    //methods and fields  
  4. }  

Understanding the simple example of inheritance

 inheritance in java

  1. class Employee{  
  2.  float salary=40000;  
  3. }  
  4. class Programmer extends Employee{  
  5.  int bonus=10000;  
  6.  public static void main(String args[]){  
  7.    Programmer p=new Programmer();  
  8.    System.out.println("Programmer salary is:"+p.salary);  
  9.    System.out.println("Bonus of Programmer is:"+p.bonus);  
  10. }  
  11. }  

 Programmer salary is:40000.0
 Bonus of programmer is:10000


Types of inheritance in java

types of inheritance in java


Note: Multiple inheritance is not supported in java through class.

multiple inheritance in java

Why multiple inheritance is not supported in java?

To reduce the complexity and simplify the language, multiple inheritance is not supported in java.
Consider a scenario where A, B and C are three classes. The C class inherits A and B classes. If A and B classes have same method and you call it from child class object, there will be ambiguity to call method of A or B class.
Since compile time errors are better than runtime errors, java renders compile time error if you inherit 2 classes. So whether you have same method or different, there will be compile time error now.
  1. class A{  
  2. void msg(){System.out.println("Hello");}  
  3. }  
  4. class B{  
  5. void msg(){System.out.println("Welcome");}  
  6. }  
  7. class C extends A,B{//suppose if it were  
  8.  Public Static void main(String args[]){  
  9.    C obj=new C();  
  10.    obj.msg();//Now which msg() method would be invoked?  
  11. }  
  12. }  

Compile Time Error