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

Inheritance in java is a mechanism in which one object acquires all the properties and behaviors of parent object.
The idea behind inheritance in java is that you can create new classes that are built upon existing classes. When you inherit from an existing class, you can reuse methods and fields of parent class, and you can add new methods and fields also.
Inheritance represents the IS-A relationship, also known as parent-child relationship.

Why use inheritance in java

• For Method Overriding (so runtime polymorphism can be achieved).
• For Code Reusability.

Syntax of Java Inheritance

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

The extends keyword indicates that you are making a new class that derives from an existing class.
In the terminology of Java, a class that is inherited is called a super class. The new class is called a subclass.

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Understanding the simple example of inheritance

 

 As displayed in the above figure, Programmer is the subclass and Employee is the superclass. Relationship between two classes is Programmer IS-A Employee.It means that Programmer is a type of Employee.

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

In the above example, Programmer object can access the field of own class as well as of Employee class i.e. code reusability.

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Types of inheritance in java

On the basis of class, there can be three types of inheritance in java: single, multilevel and hierarchical.
In java programming, multiple and hybrid inheritance is supported through interface only. We will learn about interfaces later.

 

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

When a class extends multiple classes i.e. known as multiple inheritance. For Example:

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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

Generate Prime Numbers list between 1 and 100

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package jv.prim;
/**
 * Generate Prime between 1 and 100
 * @author sm rabbi
 */
public class JvPrim {
    /**
     * @param args the command line arguments
     **/
    public static void main(String[] args) {
       
        int a,b,c;
        for(a=1;a<=100;a++)
        {
            c=1;
            for(b=2;b<=a/2;b++)
            {
                if(a%b == 0)
                {
                    c=0;
                    //System.out.println("not prime "+ a + " " + b + " " +a%b);
                    break;
                }
            }
           
            if(c==1)
            {
                System.out.println("prime= " +a);
            }
        }
    }
}
     

Sum and Count of Prime Number With Method and Parameter

Write a Java program to calculate the SUM and COUNT of Primes from a given range of numbers. Formatting required for the Input and Output statements. Use Method with Parameter and return value to the Main function.

Reference:
(1) Course Book(The Complete Reference Java j2se) ; Page 116
(2) http://c-programming-sourcecode.blogspot.com/2012/08/prime-number.html?updated-min=2012-01-01T00:00:00-08:00&updated-max=2013-01-01T00:00:00-08:00&max-results=14


Source Code:

package Prime;
import java.util.Scanner;
class PrimeCheeck
{
int sum=0;
int get_Prime_Sum(int range)
{
for(int i=1;i<=range;i++)
{
int flag=0;
for(int j=2;j<i;j++)
{
if(i%j==0)
flag=1;
}
if(flag==0)
{
System.out.print(i+" ");
sum=sum+i;
}

}
System.out.println();
return sum;
}
}
public class Prime {
public static void main(String[] args)
{
Scanner in = new Scanner(System.in);

PrimeCheeck pr =new PrimeCheeck();
int range,result;
System.out.print("Enter your last Range : ");
range = in.nextInt();
System.out.println("Sum of all prime number giving in range = " +pr.get_Prime_Sum(range));
}
}