code: protected final String getPlaceholder(final String placeholderWithDefault) {
          int separatorIdx = placeholderWithDefault.indexOf(defaultSeparator);
          if (separatorIdx == -1) {
              return placeholderWithDefault;
          }
          return placeholderWithDefault.substring(0, separatorIdx);
      }
docs: extract the placeholder name from the complete placeholder string (between prefix and separator,
  or complete placeholder if no separator is found).
  
  @param placeholderWithDefault default placeholder
  
  @return the placeholder
  
  @see #setPlaceholderPrefix
  @see #setDefaultSeparator
  @see #setPlaceholderSuffix