StringUtil.java

package org.jerlang.util;

public class StringUtil {

    /**
     * Converts a string from snake_case to CamelCase.
     */
    public static String snakeToCamelCase(String string) {
        switch (string) {
        case "io":
            return "IO";
        case "os":
            return "OS";
        case "md5":
            return "MD5";
        default:
            StringBuilder result = new StringBuilder(string.length());
            boolean capitalize = true;
            for (char c : string.toCharArray()) {
                if (c == '_') {
                    capitalize = true;
                } else if (capitalize) {
                    result.append(Character.toUpperCase(c));
                    capitalize = false;
                } else {
                    result.append(c);
                }
            }
            return result.toString();
        }
    }

    /**
     * Converts a string from CamelCase to snake_case.
     */
    public static String camelToSnakeCase(String string) {
        switch (string) {
        case "IO":
            return "io";
        case "OS":
            return "os";
        case "MD5":
            return "md5";
        default:
            StringBuilder result = new StringBuilder(string.length());
            for (char c : string.toCharArray()) {
                if (Character.isUpperCase(c)) {
                    if (result.length() > 0) {
                        result.append('_');
                    }
                    result.append(Character.toLowerCase(c));
                } else {
                    result.append(c);
                }
            }
            return result.toString();
        }
    }

}