code: public static String upperCase(final String str, final Locale locale) {
          if (str == null) {
              return null;
          }
          return str.toUpperCase(locale);
      }
docs: <p>Converts a String to upper case as per {@link String#toUpperCase(Locale)}.</p>
  
  <p>A {@code null} input String returns {@code null}.</p>
  
  <pre>
  StringUtils.upperCase(null, Locale.ENGLISH)  = null
  StringUtils.upperCase("", Locale.ENGLISH)    = ""
  StringUtils.upperCase("aBc", Locale.ENGLISH) = "ABC"
  </pre>
  
  @param str  the String to upper case, may be null
  @param locale  the locale that defines the case transformation rules, must not be null
  @return the upper cased String, {@code null} if null String input
  @since 2.5