Passing by reference in Java?

Question

In C++, if you need to have 2 objects modified, you can pass by reference. How do you accomplish this in java? Assume the 2 objects are primitive types such as int.

Answer 1

Wrap them in an object and then pass that object as a parameter to the method.

For example, the following C++ code:

bool divmod(double a, double b, double & dividend, double & remainder) {
  if(b == 0) return false;
  dividend = a / b;
  remainder = a % b;
  return true;
}

can be rewritten in Java as:

class DivRem {
  double dividend;
  double remainder;
}

boolean divmod(double a, double b, DivRem c) {
  if(b == 0) return false;
  c.dividend = a / b;
  c.remainder = a % b;
  return true;
}

Although more idiomatic style in Java would be to create and return this object from the method instead of accepting it as a parameter:

class DivRem {
  double dividend;
  double remainder;
}

DivRem divmod(double a, double b) {
  if(b == 0) throw new ArithmeticException("Divide by zero");
  DivRem c = new DivRem();
  c.dividend = a / b;
  c.remainder = a % b;
  return c;
}