Is there any simple way to convert camel-case to snake-case correctly?

Question

I tried as the below code code snippet, but the TradeID is printing as Trade_I_D, but it must be as Trade_ID.

input: getCurrency, getAccountName, getTradeID
expected output: Currency, Account_Name, Trade_ID

public class RemoveGet {

    public static void main(String args[]) {
        for (String a : args) {
            String b = a.replace("get", "");
            //System.out.println(b);
            StringBuffer sb = new StringBuffer();
            for (int i = 0; i < b.length(); i++) {
                if (Character.isUpperCase(b.charAt(i))) {
                    sb.append("_");
                    sb.append(b.charAt(i));
                } else {
                    sb.append(b.charAt(i));
                }
            }
            //System.out.println(sb.toString());
            String c = sb.toString();
            if (c.startsWith("_")) {
                System.out.println(c.substring(1));
            }
        }
    }
}

Just saying: when following java naming conventions, the correct camel case would be TradId. Which looks weird, so I get it why you prefer ID instead of Id. — GhostCat, Apr 19 '22 at 13:34
@GhostCat I think it should be `TradeId`, which looks perfectly fine to me :-) — MC Emperor, Apr 19 '22 at 14:26
Does this answer your question? [Regex for converting CamelCase to camel\_case in java](https://stackoverflow.com/questions/10310321/regex-for-converting-camelcase-to-camel-case-in-java) — TonyArra, Apr 20 '22 at 03:03

Kai-Sheng Yang · Answer 1 · 2022-04-19T11:37:31.267

1

try this

str = str.replace("get", "")
    .replaceAll("([A-Z]+)([A-Z][a-z])", "$1_$2")
    .replaceAll("([a-z])([A-Z])", "$1_$2")

edited Apr 19 '22 at 11:37

answered Apr 19 '22 at 11:16

Kai-Sheng Yang

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score 0 · Answer 2 · answered Apr 19 '22 at 11:22

Use a boolean first-time switch to only put an underscore after the second upper case letter.

Here are some test results.

getTradeID
Trade_ID

Here's the complete runnable code.

public class RemoveGet {

    public static void main(String args[]) {
        args = new String[1];
        args[0] = "getTradeID";
        
        for (String a : args) {
            System.out.println(a);
            String b = a.replace("get", "");
            boolean firstTimeSwitch = true;
//          System.out.println(b);
            StringBuffer sb = new StringBuffer();
            sb.append(b.charAt(0));
            
            for (int i = 1; i < b.length(); i++) {
                if (firstTimeSwitch && Character.isUpperCase(b.charAt(i))) {
                    sb.append("_");
                    sb.append(b.charAt(i));
                    firstTimeSwitch = false;
                } else {
                    sb.append(b.charAt(i));
                }
            }
            
            System.out.println(sb.toString());
        }
    }

}

This works absolutely correct! Thanks. But One more question is if give something like getSeparateUNderScore it is printing Separate_UNderScore but it should print Separate_UNder_Score — Sai Chand, Apr 20 '22 at 08:34
@Sai Chand: You didn't provide that specification in your original question. You need to define exactly what upper case characters need an underscore. — Gilbert Le Blanc, Apr 20 '22 at 10:14

score 0 · Answer 3 · answered Apr 19 '22 at 14:20

Instead of writing all logic in the main function, write some functions to do small tasks and call them in the main function. This makes the code readable and easy to debug. This could be the possible solution code:

public class RemoveGet {

 public static String addUnderScoreAppropriately(String input) {
     String result = "";
     String underScore = "_";
     for(int i=0; i<input.length();i++) {
         if((Character.isUpperCase(input.charAt(i))) && (i != 0)) {
             result = result + underScore + input.charAt(i);
         }else{
             result = result + input.charAt(i);
         }
     }
     result = result.replace("_I_D","_ID");
     return result;
 }

 public static void main(String args[]) {
    for (String a : args) {
        System.out.println(addUnderScoreAppropriately(a.replace("get","")));
    }
 }

}

The code will not misbehave. I have checked it for all your arguments. Check the code, test it the way you want and then ask me if you encounter any problem. — Deepeshkumar, Apr 20 '22 at 15:33

Is there any simple way to convert camel-case to snake-case correctly?

3 Answers3