private void btnTambahActionPerformed(java.awt.event.ActionEvent evt) {
                Number bil1 = (Number) ffBil1.getValue();
        Number bil2 = (Number) ffBil2.getValue();
        int b1 = bil1.intValue();
        int b2 = bil2.intValue();
        int hasil = b1 + b2;
        ffHasil.setValue(hasil);

    }

    private void btnKurangActionPerformed(java.awt.event.ActionEvent evt) {
        // TODO add your handling code here:
        Number bil1 = (Number) ffBil1.getValue();
        Number bil2 = (Number) ffBil2.getValue();
        int b1 = bil1.intValue();
        int b2 = bil2.intValue();
        int hasil = b1 - b2;
        ffHasil.setValue(hasil);

    }

    private void btnKaliActionPerformed(java.awt.event.ActionEvent evt) {
        // TODO add your handling code here:
        Number bil1 = (Number) ffBil1.getValue();
        Number bil2 = (Number) ffBil2.getValue();
        int b1 = bil1.intValue();
        int b2 = bil2.intValue();
        int hasil = b1 * b2;
        ffHasil.setValue(hasil);

    }

    private void btnBagiActionPerformed(java.awt.event.ActionEvent evt) {
        // TODO add your handling code here:
        Number bil1 = (Number) ffBil1.getValue();
        Number bil2 = (Number) ffBil2.getValue();
        int b1 = bil1.intValue();
        int b2 = bil2.intValue();
        int hasil = b1 / b2;
        ffHasil.setValue(hasil);

    }