private void DeterminantaButtonActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_DeterminantaButtonActionPerformed
     int number1, number2, number3, number4, number5, number6, number7, number8, number9;
        try {
            number1 = Integer.parseInt(
                    this.a11numberText.getText());
        } catch (NumberFormatException e) {
            JOptionPane.showMessageDialog(this, "Wrong number a11", "ERROR", JOptionPane.ERROR_MESSAGE);
            return;
        }
        try {
            number2 = Integer.parseInt(
                    this.a12numberText.getText());
        } catch (NumberFormatException e) {
            JOptionPane.showMessageDialog(this, "Wrong number a12", "ERROR", JOptionPane.ERROR_MESSAGE);
            return;
        }
        try {
            number3 = Integer.parseInt(
                    this.a13numberText.getText());
        } catch (NumberFormatException e) {
            JOptionPane.showMessageDialog(this, "Wrong number a13", "ERROR", JOptionPane.ERROR_MESSAGE);
            return;
        }
        try {
            number4 = Integer.parseInt(
                    this.a21numberText.getText());
        }
        catch (NumberFormatException e){
            JOptionPane.showMessageDialog(this, "Wrong number a21", "ERROR", JOptionPane.ERROR_MESSAGE);
            return;
        }
        try {
            number5 = Integer.parseInt(
                    this.a22numberText.getText());
        }
        catch (NumberFormatException e){
            JOptionPane.showMessageDialog(this, "Wrong number a22", "ERROR", JOptionPane.ERROR_MESSAGE);
            return;
        }
        try {
            number6 = Integer.parseInt(
                    this.a23numberText.getText());
        }
        catch (NumberFormatException e){
            JOptionPane.showMessageDialog(this, "Wrong number a23", "ERROR", JOptionPane.ERROR_MESSAGE);
            return;
        }
        try {
            number7 = Integer.parseInt(
                    this.a31numberText.getText());
        }
        catch (NumberFormatException e){
            JOptionPane.showMessageDialog(this, "Wrong number a31", "ERROR", JOptionPane.ERROR_MESSAGE);
            return;
        }
        try {
            number8 = Integer.parseInt(
                    this.a32numberText.getText());
        }
        catch (NumberFormatException e){
            JOptionPane.showMessageDialog(this, "Wrong number a32", "ERROR", JOptionPane.ERROR_MESSAGE);
            return;
        }
        try {
            number9 = Integer.parseInt(
                    this.a33numberText.getText());
        }
        catch (NumberFormatException e){
            JOptionPane.showMessageDialog(this, "Wrong number a33", "ERROR", JOptionPane.ERROR_MESSAGE);
            return;
        }
        int Rezultat = number1 *(number5 * number9 - number6 * number8)- number2 * (number4 * number9 - number6 * number7)+ number3 *(number4 * number8 - number5 * number7);
              this.ResenjeLabel2.setText(
                      " "+ Rezultat);
    }//GEN-LAST:event_DeterminantaButtonActionPerformed