Perhitungan sederhana menggunakan Java

public class penjumlahan extends javax.swing.JFrame {
 int nilai1;
int nilai2;
int nilai3;
String Hasil;

    public penjumlahan() {
        initComponents();
    }
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                         
    private void initComponents() {

        jLabel1 = new javax.swing.JLabel();
        jLabel2 = new javax.swing.JLabel();
        tfnilai2 = new javax.swing.JTextField();
        btntmbah = new javax.swing.JButton();
        btnkurang = new javax.swing.JButton();
        btnkali = new javax.swing.JButton();
        lbltambah = new javax.swing.JLabel();
        tfnilai1 = new javax.swing.JTextField();
        lblkurang = new javax.swing.JLabel();
        lblkali = new javax.swing.JLabel();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jLabel1.setText("Nilai 1 : ");

        jLabel2.setText("Nilai 2 : ");

        btntmbah.setText("+");
        btntmbah.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btntmbahActionPerformed(evt);
            }
        });

        btnkurang.setText("-");
        btnkurang.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btnkurangActionPerformed(evt);
            }
        });

        btnkali.setText("*");
        btnkali.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btnkaliActionPerformed(evt);
            }
        });

        lbltambah.setText("Hasil Penjumlahan");

        tfnilai1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                tfnilai1ActionPerformed(evt);
            }
        });

        lblkurang.setText("Hasil Pengurangan");

        lblkali.setText("Hasil Perkalian");

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(31, 31, 31)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(layout.createSequentialGroup()
                        .addComponent(btntmbah)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                        .addComponent(lbltambah))
                    .addGroup(layout.createSequentialGroup()
                        .addComponent(jLabel2)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addComponent(tfnilai2, javax.swing.GroupLayout.PREFERRED_SIZE, 175, javax.swing.GroupLayout.PREFERRED_SIZE))
                    .addGroup(layout.createSequentialGroup()
                        .addComponent(jLabel1)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addComponent(tfnilai1, javax.swing.GroupLayout.PREFERRED_SIZE, 175, javax.swing.GroupLayout.PREFERRED_SIZE))
                    .addGroup(layout.createSequentialGroup()
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                            .addComponent(btnkali)
                            .addComponent(btnkurang))
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addComponent(lblkali)
                            .addComponent(lblkurang))))
                .addContainerGap(152, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(19, 19, 19)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel1)
                    .addComponent(tfnilai1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel2)
                    .addComponent(tfnilai2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(32, 32, 32)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(btntmbah)
                    .addComponent(lbltambah))
                .addGap(5, 5, 5)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(btnkurang)
                    .addComponent(lblkurang))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(btnkali)
                    .addComponent(lblkali))
                .addContainerGap(123, Short.MAX_VALUE))
        );

        pack();
    }// </editor-fold>                       

private void btntmbahActionPerformed(java.awt.event.ActionEvent evt) {                                        
// TODO add your handling code here:
    nilai1=Integer.valueOf(tfnilai1.getText());
nilai2=Integer.valueOf(tfnilai2.getText());
nilai3=nilai1 + nilai2;
        Hasil=String.valueOf(nilai3);
lbltambah.setText("Hasil Penjumlahan: \t\t\t" + Hasil);  
}                                       

private void btnkurangActionPerformed(java.awt.event.ActionEvent evt) {                                         
// TODO add your handling code here:
    nilai1=Integer.valueOf(tfnilai1.getText());
nilai2=Integer.valueOf(tfnilai2.getText());
nilai3=nilai1 - nilai2;
        Hasil=String.valueOf(nilai3);
lblkurang.setText("Hasil Pengurangan: \t\t\t" + Hasil);
}                                        

private void btnkaliActionPerformed(java.awt.event.ActionEvent evt) {                                       
// TODO add your handling code here:
    nilai1=Integer.valueOf(tfnilai1.getText());
nilai2=Integer.valueOf(tfnilai2.getText());
nilai3=nilai1 * nilai2;
        Hasil=String.valueOf(nilai3);
lblkali.setText("Hasil Perkalian: \t\t\t" + Hasil);
}                                      

private void tfnilai1ActionPerformed(java.awt.event.ActionEvent evt) {                                        
    // TODO add your handling code here:
}                                       

    public static void main(String args[]) {
       
        java.awt.EventQueue.invokeLater(new Runnable() {

            public void run() {
                new penjumlahan().setVisible(true);
            }
        });
    }
    // Variables declaration - do not modify                    
    private javax.swing.JButton btnkali;
    private javax.swing.JButton btnkurang;
    private javax.swing.JButton btntmbah;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel lblkali;
    private javax.swing.JLabel lblkurang;
    private javax.swing.JLabel lbltambah;
    private javax.swing.JTextField tfnilai1;
    private javax.swing.JTextField tfnilai2;
    // End of variables declaration                  
}