code: public void append(final char ch) {
          final int newlen = this.len + 1;
          if (newlen > this.array.length) {
              expand(newlen);
          }
          this.array[this.len] = ch;
          this.len = newlen;
      }
docs: Appends {@code ch} char to this buffer. The capacity of the buffer
  is increased, if necessary, to accommodate the additional char.
  
  @param   ch        the char to be appended.