ebean/src/main/java/io/ebean/util/CamelCaseHelper.java

package io.ebean.util;

public class CamelCaseHelper {

  /**
   * To underscore from camel case using digits compressed true and force upper case false.
   */
  public static String toUnderscoreFromCamel(String camelCase) {
    return toUnderscoreFromCamel(camelCase, true, false);
  }

  /**
   * Convert and return the string to underscore from camel case.
   */
  public static String toUnderscoreFromCamel(String camelCase, boolean digitsCompressed, boolean forceUpperCase) {

    int lastUpper = -1;
    StringBuilder sb = new StringBuilder(camelCase.length() + 4);
    for (int i = 0; i < camelCase.length(); i++) {
      char c = camelCase.charAt(i);

      if ('_' == c) {
        // Underscores should just be passed through
        sb.append(c);
        lastUpper = i;
      } else if (Character.isDigit(c)) {
        if (i > lastUpper + 1 && !digitsCompressed) {
          sb.append("_");
        }
        sb.append(c);
        lastUpper = i;

      } else if (Character.isUpperCase(c)) {
        if (i > lastUpper + 1) {
          sb.append("_");
        }
        sb.append(Character.toLowerCase(c));
        lastUpper = i;

      } else {
        sb.append(c);
      }
    }
    String ret = sb.toString();
    if (forceUpperCase) {
      ret = ret.toUpperCase();
    }
    return ret;
  }

  /**
   * To camel from underscore.
   *
   * @param underscore the underscore
   * @return the string
   */
  public static String toCamelFromUnderscore(String underscore) {

    String[] vals = underscore.split("_");
    if (vals.length == 1) {
      return isUpperCase(underscore) ? underscore.toLowerCase() : underscore;
    }

    StringBuilder result = new StringBuilder();
    for (int i = 0; i < vals.length; i++) {
      String lower = vals[i].toLowerCase();
      if (i > 0) {
        char c = Character.toUpperCase(lower.charAt(0));
        result.append(c);
        result.append(lower.substring(1));
      } else {
        result.append(lower);
      }
    }

    return result.toString();
  }

  private static boolean isUpperCase(String underscore) {
    for (int i = 0; i < underscore.length(); i++) {
      if (Character.isLowerCase(underscore.charAt(i))) {
        return false;
      }
    }
    return true;
  }
}