public class ComplexCalc {
  public static void main(String[] args) {
    Complex c1 = new Complex();
    Complex c2 = new Complex(1,3);
    Complex c3 = c1.add(c2);
    System.out.println(c2.add(c1));
    System.out.println(Complex.add(c1,c3));
    
    // Can you do this?
    // c1.real = 4;
    
  }
}

class Complex {
  private double real; // real component
  private double imag; // imaginary component
  public Complex() { }
  public Complex(double r, double i) { real = r; imag = i; }
  
  // Add two complex numbers together (one approach):
  public Complex add(Complex other) {
    return new Complex(real+other.real, imag+other.imag);
  }
  
  // Alternative approach:
  public static Complex add(Complex c1, Complex c2) {
    return new Complex(c1.real+c2.real,c2.real+c2.imag);
  }
  
  // Stringify complex number:
  public String toString() {
    return real+"+"+imag+"i"; // what if imag is neg?
  }
}