How do I convert number to a letter in Java?

Question

I want to make a program to convert number to letter, from 0-9 to ABCDEFGHIK. For example: with n = 10 the output would be BA as 0 is A is 0 and B is 1. Here is my code:

String convertNumber(long n) {
    String result="";
    String strN = Long.toString(n);
    for (int i=0; i < strN.length();i++){
        char ch = strN.charAt(i);
        switch(ch){
            case '0':
            result = "A";
            case '1':
            result = "B";
            case '2':
            result = "C";
            case '3':
            result = "D";
            case '4':
            result = "E";
            case '5':
            result = "F";
            case '6':
            result = "G";
            case '7':
            result = "H";
            case '8':
            result = "I";
            case '9':
            result = "K";
        }
    }
    return result;
}

However, the results returns only K. Where did I do wrong? Thank you!

Does this answer your question? [How do I convert a number to a letter in Java?](https://stackoverflow.com/questions/10813154/how-do-i-convert-a-number-to-a-letter-in-java) — Renato, May 08 '20 at 14:13
You need to break after each case or you will 'fall through' to the next case. In your swtich, there are no breaks so it will always fall through to the last case. — vsfDawg, May 08 '20 at 14:14

0xh3xa · Answer 1 · 2020-05-08T14:38:34.717

0

You can use this one:

static String convertNumber(int n) {
        int reminder;
        char[] arr = "ABCDEFGHIK".toCharArray();
        int len = arr.length;
        StringBuilder builder = new StringBuilder();
        while (n != 0) {
            reminder = (int) n % 10;
            n /= 10;
            builder.append(arr[(reminder % len)]);
        }
        return builder.toString();
    }

, main

  static public void main(String[] args) {
        System.out.println(convertNumber(65));
        System.out.println(convertNumber(78));
        System.out.println(convertNumber(99));
        System.out.println(convertNumber(901));
  }

, output

FG
IH
KK
BAK

edited May 08 '20 at 14:38

answered May 08 '20 at 14:17

0xh3xa

4,801
2
14
28

Thank you for helping! I would have time to check my code xD Luv u – ImStuck May 08 '20 at 14:28
You are welcome :) – 0xh3xa May 08 '20 at 14:32
actually i just have a check in your code. It seems like 6,7,8,9 has the wrong letter. – ImStuck May 08 '20 at 14:36
because you mentioned in your post that the characters in `ABCDEFJIK` I have updated to `ABCDEFGHIK` – 0xh3xa May 08 '20 at 14:42
oh its mine that wrong, oops mb.... – ImStuck May 08 '20 at 14:44
No problem, just figure out what' s the problem :D – 0xh3xa May 08 '20 at 14:45

Arvind Kumar Avinash · Accepted Answer · 2020-05-08T14:31:39.223

There are three mistakes in your program:

Not using break with the case and therefore every case will fall to the last case.
Using = instead of +=
Using the loop in reverse order than the required order. It should be for (int i = strN.length() - 1; i >= 0; i--) instead of for (int i=0; i < strN.length();i++)

Given below is your corrected program:

public class Main {
    public static void main(String[] args) {
        System.out.println(convertNumber(10));
    }

    static String convertNumber(long n) {
        String result = "";
        String strN = Long.toString(n);
        for (int i = strN.length() - 1; i >= 0; i--) {
            char ch = strN.charAt(i);
            switch (ch) {
            case '0':
                result += "A";
                break;
            case '1':
                result += "B";
                break;
            case '2':
                result += "C";
                break;
            case '3':
                result += "D";
                break;
            case '4':
                result += "E";
                break;
            case '5':
                result += "F";
                break;
            case '6':
                result += "G";
                break;
            case '7':
                result += "H";
                break;
            case '8':
                result = "I";
                break;
            case '9':
                result = "K";
            }
        }
        return result;
    }
}

Output:

AB

score 0 · Answer 3 · edited May 08 '20 at 17:57

0

You forgot the break. add break; in every case, like this:

case '0': result = "A"; break; case '1': result = "B"; break;

edited May 08 '20 at 17:57

Marit

2,399
18
27

answered May 08 '20 at 14:29

Shouko

1

How do I convert number to a letter in Java?

3 Answers3