Converting grade in a for loops

Question

I have following code:

public static void main(String[] args) {
        convert13to7(7);

    }

    public static int convert13to7(int grade) {
        int newGrade = 0;
        int[] scale13 = {00, 03, 5, 6, 7, 8, 9, 10, 11, 13};
        int[] scale7 =  {-3, 00, 00, 02, 4, 7, 7, 10, 12, 12};

        for (int i = 0; i < scale13.length; i++) {
            if (grade == scale13[i]) {
            newGrade = scale7[i];
            }
        }
    return newGrade;
    }

The point of this code is to convert an old danish grade scale to a new one but the problem is that I don't get any output when using the convert13to7 function. Does anyone see the issue here?

you have to print the returned value of `convert13to7(7)` is you wish to see it. — Eran, Sep 24 '19 at 07:39
Replace `convert13to7(7);` with `System.out.println(convert13to7(7));`. — howlger, Sep 24 '19 at 07:41
You're just calling your function, you never show the result, use a `System.out.println(convert13to7(7));` in your main for example — AKMMM, Sep 24 '19 at 07:41
Oh I see, that was some rookie mistake. Thanks for the help, guys! — nostres97, Sep 24 '19 at 07:42
Possible duplicate of [Java string method not returning string](https://stackoverflow.com/questions/58051454/java-string-method-not-returning-string) — Hans Keﬆing, Sep 24 '19 at 07:47

Andrew Tobilko · Answer 1 · 2019-09-24T07:53:13.320

4

convert13to7 produces a converted value, it doesn't print it.

System.out.println(convert13to7(7));

Other small issues:

The method name isn't clear.
You don't necessarily need to initialise those two arrays every time the method is called.
Think about validation. Returning a 0 if you've failed to convert the input is not a good option.
Think about List.indexOf. It's simpler and more intuitive.

edited Sep 24 '19 at 07:53

answered Sep 24 '19 at 07:41

Andrew Tobilko

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score 1 · Answer 2 · answered Sep 24 '19 at 08:04

To print the result, use System.out.println():

int grade = convert13to7(7);
System.out.println(grade);

I would recommend you to use Map, not to iterate every time over an array:

public final class GradeConverter {

    private final Map<Integer, Integer> map13to7 = new HashMap<>();

    {
        map13to7.put(0, -3);
        map13to7.put(3, 0);
        map13to7.put(5, 0);
        map13to7.put(6, 2);
        map13to7.put(7, 4);
        map13to7.put(8, 7);
        map13to7.put(9, 7);
        map13to7.put(10, 10);
        map13to7.put(11, 12);
        map13to7.put(13, 12);
    }

    public int convert10to7(int grade) {
        return map13to7.getOrDefault(grade, 0);
    }

}

Next point, pay attention to writing 03 instead of 3 because in Java 0 prefix is a marker of the octal system. E.g. 077 is a decimal value 63.

score 0 · Answer 3 · answered Sep 24 '19 at 07:48

You need to collect the output where you have called the method.

package com;

public class Test{
    public static void main(String[] args) {
        // collect output here
        int newGrade = convert13to7(7);
        System.out.println(newGrade);
    }

    public static int convert13to7(int grade) {
        int newGrade = 0;
        int[] scale13 = {00, 03, 5, 6, 7, 8, 9, 10, 11, 13};
        int[] scale7 =  {-3, 00, 00, 02, 4, 7, 7, 10, 12, 12};

        for (int i = 0; i < scale13.length; i++) {
            if (grade == scale13[i]) {
            newGrade = scale7[i];
            }
        }
        // alternatively you can print output here
        System.out.println(newGrade);
    return newGrade;
    }

}

score 0 · Answer 4 · answered Sep 24 '19 at 08:13

Hei,

You need to save the output in main or just to print it if you don't need to use it.

public static void main(String[] args) {
    convert13to7(7);
}

Replace with

public static void main(String[] args) {
    //if you want just to check the output
    System.out.println(convert13to7(7));

    //or if you want to use it further
    int holdValue = convert13to7(7);
}

You also should handle exceptions ( at least ArrayIndexOutOfBoundsException). Here is an example using lambda (almost the same thing)

interface lambda{
   int getGrades(int[] scale13, int[] scale7, int grade);
}

public class Grades{
    public static void main(String[] args) {

    lambda output = (int[] scale13, int[] scale7, int grade) ->{
        int newGrade = 0;
        try {
            for (int i = 0; i < scale13.length; i++) 
                if (grade == scale13[i]) 
                    newGrade = scale7[i];
        }catch(ArrayIndexOutOfBoundsException e) {
            System.out.println("ArrayIndexOutOfBoundsException Exeption.");
        }

        return newGrade;
    };

    int[] scale13 = {00, 03, 5, 6, 7, 8, 9, 10, 11, 13};
    int[] scale7 =  {-3, 00, 00, 02, 4, 7, 7, 10, 12, 12};

    System.out.println(output.getGrades(scale13, scale7, 7));

}

}

Converting grade in a for loops

4 Answers4