code: public static boolean isAllUpperCase(final String cs) {
          if (Strings.isNullOrEmpty(cs)) {
              return false;
          }
          final int sz = cs.length();
          for (int i = 0; i < sz; i++) {
              if (!Character.isUpperCase(cs.charAt(i))) {
                  return false;
              }
          }
          return true;
      }
docs: <p>Checks if the CharSequence contains only uppercase characters.
  
  <p>{@code null} will return {@code false}.
  An empty String (length()=0) will return {@code false}.
  
  <pre>
  StringUtils.isAllUpperCase(null)   = false
  StringUtils.isAllUpperCase("")     = false
  StringUtils.isAllUpperCase("  ")   = false
  StringUtils.isAllUpperCase("ABC")  = true
  StringUtils.isAllUpperCase("aBC")  = false
  StringUtils.isAllUpperCase("A C")  = false
  StringUtils.isAllUpperCase("A1C")  = false
  StringUtils.isAllUpperCase("A/C")  = false
  </pre>
  
  @param cs the CharSequence to check, may be null
  @return {@code true} if only contains uppercase characters, and is non-null
  @since 2.5
  @since 3.0 Changed signature from isAllUpperCase(String) to isAllUpperCase(CharSequence)