What is the most elegant way to convert a hyphen separated word (e.g. “do-some-stuff”) to the lower camel-case variation (e.g. “doSomeStuff”)?

Question

What is the most elegant way to convert a hyphen separated word (e.g. \"do-some-stuff\") to the lower camel-case variation (e.g. \"doSomeStuff\") in Java?

Answer 1

With Java 8 there is finally a one-liner:

Arrays.stream(name.split("\\-"))
    .map(s -> Character.toUpperCase(s.charAt(0)) + s.substring(1).toLowerCase())
    .collect(Collectors.joining());

Though it takes splitting over 3 actual lines to be legible ツ

(Note: "\\-" is for kebab-case as per question, for snake_case simply change to "_")

Answer 2

For those who has com.fasterxml.jackson library in the project and don't want to add guava you can use the jaskson namingStrategy method:

new PropertyNamingStrategy.SnakeCaseStrategy.translate(String);

Answer 3

Here is a slight variation of Andreas' answer that does more than the OP asked for:

public static String toJavaMethodName(final String nonJavaMethodName){
    final StringBuilder nameBuilder = new StringBuilder();
    boolean capitalizeNextChar = false;
    boolean first = true;

    for(int i = 0; i < nonJavaMethodName.length(); i++){
        final char c = nonJavaMethodName.charAt(i);
        if(!Character.isLetterOrDigit(c)){
            if(!first){
                capitalizeNextChar = true;
            }
        } else{
            nameBuilder.append(capitalizeNextChar
                ? Character.toUpperCase(c)
                : Character.toLowerCase(c));
            capitalizeNextChar = false;
            first = false;
        }
    }
    return nameBuilder.toString();
}

It handles a few special cases:

• fUnnY-cASe is converted to funnyCase
• --dash-before-and--after- is converted to dashBeforeAndAfter
• some.other$funky:chars? is converted to someOtherFunkyChars

Answer 4

As I'm not a big fan of adding a library just for one method, I implemented my own solution (from camel case to snake case):

public String toSnakeCase(String name) {
    StringBuilder buffer = new StringBuilder();
    for(int i = 0; i < name.length(); i++) {
        if(Character.isUpperCase(name.charAt(i))) {
            if(i > 0) {
                buffer.append('_');
            }
            buffer.append(Character.toLowerCase(name.charAt(i)));
        } else {
            buffer.append(name.charAt(i));
        }
    }
    return buffer.toString();
}

Needs to be adapted depending of the in / out cases.

Answer 5

get The Apache commons jar for StringUtils. Then you can use the capitalize method

import org.apache.commons.lang.StringUtils;
public class MyClass{

    public String myMethod(String str) {
        StringBuffer buff = new StringBuffer();

        String[] tokens = str.split("-");
        for (String i : tokens) {
            buff.append(StringUtils.capitalize(i));
        }

        return buff.toString();
    }
}