public void changeProfessor() {

        int actualRound = Sims_1._maingame.round;

        if (actualRound == 4) {
            lectorChanged4 = true; //shows that professor was changed on the beginning of the 2.Semester (4.Round)
            Sims_1._maingame.professor = (int) Math.round(Math.random() * 100 + 1);
        } else if (actualRound == 7) {
            lectorChanged7 = true;
            Sims_1._maingame.professor = (int) Math.round(Math.random() * 100 + 1);
        } else if (actualRound == 10) {
            lectorChanged10 = true;
            Sims_1._maingame.professor = (int) Math.round(Math.random() * 100 + 1);
        } else if (actualRound == 13) {
            lectorChanged13 = true;
            Sims_1._maingame.professor = (int) Math.round(Math.random() * 100 + 1);
        } else if (actualRound == 16) {
            lectorChanged16 = true;
            Sims_1._maingame.professor = (int) Math.round(Math.random() * 100 + 1);
        }
        //setting new professor icon        
        //temp is a temporar variable needed for comparison 
        int temp;                       //fix by Dawid
        while ((temp = (int) Math.round(Math.random() * 2)) == Sims_1._maingame.professorIconNum);

//         String temp=Sims_1._maingame.professorIconPath[((int) Math.round(Math.random()*2 ))];
//         
//        //elimination of setting the same professor picture as before
//          while (Sims_1._maingame.professorIcon.equals(temp)){
//              temp=Sims_1._maingame.professorIconPath[((int) Math.round(Math.random()*2 ))];                  
//        }
        Sims_1._maingame.professorIconNum = temp;
        Sims_1._maingame.professorIcon = Sims_1._maingame.professorIconPath[temp];

        //loading new icon on the button
        this.professorButton.setIcon(new ImageIcon(getClass().getResource(Sims_1._maingame.professorIcon)));
        this.professorButton.updateUI();

        //  System.out.println("Dozent wurde gewechselt. Neuer Dozentenwert: " + Sims_1._maingame.professor);
        professorCounter.setText("0x"); //label update
        professorCounter.repaint();
    }