Calcular el sueldo de un empleado en Jframe

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                       
        String entrada=this.jTextField1.getText();
        double pph=Double.parseDouble(entrada);
        entrada = this.jTextField2.getText();
        double ht=Double.parseDouble(entrada);
        double aum=0,sn=0;
        double sb=ht*pph;
        String regalo = null;
        if(sb>=200 && sb<=500)
        {aum=sb*0.03;
         regalo="Un Polo";
        }
        if (sb>=501 && sb<=1000)
            {aum=sb*0.05;
         regalo="memoria USB 8GB";
        }
        if (sb>1000)
        {aum=sb*0.08;
         regalo="Celular Multimedia";
        }
        sn=sb+aum;
        this.jTextField3.setText(""+sb);
        this.jTextField4.setText(""+aum);
        this.jTextField5.setText(""+regalo);
        this.jTextField6.setText(""+sn);
    }