Aufgabe 1 ideone

/* package whatever; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

class Ideone{
	public static void main(String[] args) {
 		Complex c1 = new Complex(2, 2);
       	Complex c2 = new Complex(4, 3);

       	c1.print(); // 2+2i
       	c2.print(); // 4+3i

       	c1.add(c2);
       	c2.mul(c1);
      	c2.print();
       	c2.sub(c1);

       	c1.print(); // 6+5i
       	c2.print(); // 3+33i
       	}
}

class Complex{
  public int real;
  public int imaginary;

  public Complex(int r, int i){
    this.real = r;
    this.imaginary = i;
  }

  public void print(){
    System.out.print(this.real + "+" + this.imaginary + "i \n");
   }

  public void add(Complex c){
    this.real += c.real;
    this.imaginary += c.imaginary;
  }

  public void mul(Complex c){
    int oldreal = this.real;
    this.real = this.real * c.real - this.imaginary * c.imaginary;
    this.imaginary = oldreal * c.imaginary + this.imaginary * c.real;
  }

  public void sub(Complex c){
    this.real -= c.real;
    this.imaginary =this.imaginary- c.imaginary;
  }
}