Java Tech - Chapter 3 : Science & Engineering

Fortran includes a complex number type but Java unfortunately does not. We can, though, create a complex class of our own. A class type will not perform at the speed of a primitive type but should otherwise work just as well.

A complex number needs two memory locations reserved for the real and imaginary parts and it must provide methods to perform operations on these values and with the values of other instances of the complex number class.

BasicComplex.java

public class BasicComplex
{
  //Properties
  double real;
  double img;

  // Constructor that initializes
  // the values
  BasicComplex (double r, double i)
  { real = r; img = i; }

  // Define an add method
  public void add (BasicComplex cvalue) {
    real = real + cvalue.real;
    img = img  + cvalue.img;
  }

  // Define a subtract method
  public void subtract (BasicComplex cvalue) {
    real = real - cvalue.real;
    img = img  - cvalue.img;
  }
}

The BasicComplex class holds the real and imaginary parts in two double type instance variables. Since this class is only for demonstration purposes, it includes just two methods. An instance of the class can add/subtract another instance of the class to/from itself. (A practical complex number class would obviously need methods to provide the absolute value of the complex number, multiplication, division, etc.).

We could use such a class as follows where we create 2 instances of our complex class and then add them together:

public class complexTest {
  static public void main (String [] args) {
   // Create complex objects
   BasicComplex a = new BasicComplex (1,2);
   BasicComplex b = new BasicComplex (3,1);

   a.add(b); // a now holds a+b
     ...

}
}

This class is very limited. In Chapter 4: Tech : Complex Class we will add more features to a complex class, taking advantage of class features such as overloading of methods.

However, this example does illustrate some of the basic concepts of classes: how classes relate to data types, and how classes can be used in mathematical applications.