public java.lang.StringBuffer append(java.lang.String str){
  internal.append(str);
  return this;
}

public java . lang . StringBuffer append ( java . lang . String str ) { internal . append ( str ) ; return this ; }
appends the string to this string buffer . the characters of the string argument are appended , in order , to the contents of this string buffer , increasing the length of this string buffer by the length of the argument . if str is null , then the four characters " null " are appended to this string buffer . let n be the length of the old character sequence , the one contained in the string buffer just prior to execution of the append method . then the character at index k in the new character sequence is equal to the character at index k in the old character sequence , if k is less than n ; otherwise , it is equal to the character at index k - n in the argument str .
