public java.lang.StringBuilder insert(int offset,java.lang.Object obj){
  return insert(offset,obj.toString());
}

public java . lang . StringBuilder insert ( int offset , java . lang . Object obj ) { return insert ( offset , obj . toString ( ) ) ; }
inserts the string representation of the object argument into this string buffer . the second argument is converted to a string as if by the method string . valueof , and the characters of that string are then inserted into this string buffer at the indicated offset . the offset argument must be greater than or equal to 0 , and less than or equal to the length of this string buffer .
