code: public boolean contains(final char ch) {
          final char[] thisBuf = buffer;
          for (int i = 0; i < this.size; i++) {
              if (thisBuf[i] == ch) {
                  return true;
              }
          }
          return false;
      }
docs: Checks if the string builder contains the specified char.
  
  @param ch  the character to find
  @return true if the builder contains the character