getting 0 output instead of correct output

Question

I can put the input but in output, I got a result of zero. I am using two class one is main which is logbook and another one is grade calculation. In grade calculator, I have written method and constructor and in logbook, class calling those methods through the constructor.

import java.util.Scanner;

public class LogBook  { 
    public static void main(String[] args) {
        GradeCalculation g = new GradeCalculation();
        g.Askmarks();
        g.finalmark();
    }
}

import java.util.Scanner;

public class GradeCalculation {
    Scanner kb = new Scanner(System.in);

    private double quiz, midsemester, appliedproject, finaltest, finalmarks;

    GradeCalculation(double quiz, double midsemester, double appliedproject, double finaltest, double finalmarks){
    }

    GradeCalculation(){

    }

    public void Askmarks(){
        System.out.print("Enter the QUIZ marks: ");
        double quiz = kb.nextDouble();
        System.out.print("Enter the midsemester marks: "); 
        double midsemester = kb.nextDouble();
        System.out.print("Enter the appliedproject: ");
        double appliedproject = kb.nextDouble();
        System.out.print("Enter the finaltest: ");  
        double finaltest = kb.nextDouble();
    }

    public void finalmark(){
        finalmarks= 0.1*(quiz)+0.2*(midsemester)+0.4*(appliedproject)+0.3*(finaltest);
        System.out.print("Enter the final: " + finalmarks);  
    }   
}

Answer 1

The problem is that you were defining local variables in Askmarks

double quiz = kb.nextDouble();
...
double finaltest = kb.nextDouble();

They don't affect the fields

private double quiz, midsemester ,appliedproject ,finaltest,finalmarks;

and, therefore, in finalmark , you are getting the default value for each double field, which is 0.0 .

The solution would be setting the fields rather than initializing local variables .

this.quiz = kb.nextDouble();
...
this.finaltest = kb.nextDouble();

Answer 2

In your Askmarks method, you are redefining the variables by prefacing them with double . If you remove the doubles from your Askmarks method, it should work.

public void Askmarks(){
    System.out.print("Enter the QUIZ marks: ");
    quiz = kb.nextDouble();
    System.out.print("Enter the midsemester marks: "); 
    midsemester = kb.nextDouble();
    System.out.print("Enter the appliedproject: ");
    appliedproject = kb.nextDouble();
    System.out.print("Enter the finaltest: ");  
    finaltest = kb.nextDouble();
}

Answer 3

You're shadowing your fields in GradeCalculation in Askmarks() . Remove the type declarations of the variables inside the function. So, instead of:

...
double quiz = kb.nextDouble();
...

You should use:

...
quiz = kb.nextDouble();
...

or

...
this.quiz = kb.nextDouble();
...

---

What you are doing with:

...
double quiz = kb.nextDouble();
...
double midsemester = kb.nextDouble();
...

is that you are shadowing the class fields with the same name (eg double quiz is going to shadow the class's quiz ). Shadowing refers to the behaviour in which a variable declared and/or initialized within some scope "replaces" another variable of the same name residing in an outer scope.

In your case, Askmarks() will now think that, for example, quiz is a local variable that only exists inside the function, and the class field quiz no longer exists in its viewpoint.