public java.lang.StringBuffer reverse(){
  internal=internal.reverse();
  return this;
}

public java . lang . StringBuffer reverse ( ) { internal = internal . reverse ( ) ; return this ; }
the character sequence contained in this string buffer is replaced by the reverse of the sequence . let n be the length of the old character sequence , the one contained in the string buffer just prior to execution of the reverse method . then the character at index k in the new character sequence is equal to the character at index n - k - 1 in the old character sequence .
