java - Rational class writing add and multiply methods -

this continuation of question posted last week i'm still having trouble with. i'm trying write rational class containing 2 private instance variables num , den datatype biginteger. rational constructor takes 2 int's parameters.

problem whenever write add or multiply method in rational class eclipse gives me error. don't know why give me error. understand it, operators +, -, *, / can used on primitive datatypes , since private instance variables biginteger's nonpprimitive datatypes , addition or multiplication have done through add or multiply method.

code below gives me error don't know why. don't understand what's conceptually wrong code. reason error conceptual using this.num/this.den/r.num/r.den in methods or error have related syntax? error add , multiply methods same , says "the constructor rational(biginteger,biginteger) undefined".

public class rational{     public rational(int x, int y) {       num = biginteger.valueof(x);       den = biginteger.valueof(y);  }    public rational add(rational r) {      return new rational(this.num.multiply(r.den).add(r.num.multiply(this.den)), this.den.multiply(r.den)); }   public rational multiply(rational r) {       return new rational(this.num.multiply(r.num), this.den.multiply(r.den)); }   private biginteger num; private biginteger den } 

the constructor have defined, takes 2 ints arguments.

 public rational(int x, int y) {       num = biginteger.valueof(x);       den = biginteger.valueof(y);  } 

and compiler complains because passing 2 bigintegers.

have new overloaded constructor

 public rational(biginteger x, biginteger y) {       num = x;       den = y;  }