Calcul TVA en java

ce ne sont même pas des chaînes de caractères

NombreTfd et TvaTfd, ces deux élément ont tout l'air d'être des éléments GUI (d'affichage)

voici le code complet


/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/

/*
* Main.java
*
* Created on 18 janv. 2012, 05:32:28
*/
package Index;

/**
*
* @author
*/
public class Main extends javax.swing.JFrame {

/** Creates new form Main */
public Main() {
initComponents();
}

/** This method is called from within the constructor to
* initialize the form.
* WARNING: Do NOT modify this code. The content of this method is
* always regenerated by the Form Editor.
*/
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {

jPanel1 = new javax.swing.JPanel();
NombreTfd = new javax.swing.JTextField();
TvaTfd = new javax.swing.JTextField();
HTbtn = new javax.swing.JButton();
TTCBtn = new javax.swing.JButton();
TotalLbl = new javax.swing.JLabel();
jLabel3 = new javax.swing.JLabel();

setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

jPanel1.setBackground(new java.awt.Color(0, 153, 153));

NombreTfd.setHorizontalAlignment(javax.swing.JTextField.CENTER);

HTbtn.setBackground(new java.awt.Color(0, 153, 255));
HTbtn.setText("HT");
HTbtn.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
HTbtnActionPerformed(evt);
}
});

TTCBtn.setBackground(new java.awt.Color(0, 153, 255));
TTCBtn.setText("TTC");
TTCBtn.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
TTCBtnActionPerformed(evt);
}
});

TotalLbl.setHorizontalAlignment(javax.swing.SwingConstants.RIGHT);
TotalLbl.setText("0,00");

jLabel3.setText("Entrer un nombre");

javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
jPanel1.setLayout(jPanel1Layout);
jPanel1Layout.setHorizontalGroup(
jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel1Layout.createSequentialGroup()
.addContainerGap(149, Short.MAX_VALUE)
.addComponent(jLabel3)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
.addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false)
.addComponent(TvaTfd, javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(TotalLbl, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
.addGroup(jPanel1Layout.createSequentialGroup()
.addComponent(HTbtn)
.addGap(18, 18, 18)
.addComponent(TTCBtn))
.addComponent(NombreTfd, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, 114, Short.MAX_VALUE))
.addGap(43, 43, 43))
);
jPanel1Layout.setVerticalGroup(
jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(jPanel1Layout.createSequentialGroup()
.addGap(63, 63, 63)
.addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(NombreTfd, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(jLabel3))
.addGap(38, 38, 38)
.addComponent(TvaTfd, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addGap(18, 18, 18)
.addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(HTbtn)
.addComponent(TTCBtn))
.addGap(37, 37, 37)
.addComponent(TotalLbl)
.addContainerGap(67, Short.MAX_VALUE))
);

javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
);

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

private void HTbtnActionPerformed(java.awt.event.ActionEvent evt) {
String nombre = NombreTfd.getText();
String taux = TvaTfd.getText();
TotalLbl = (NombreTfd*TvaTfd);

}

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

/**
* @param args the command line arguments
*/
public static void main(String args[]) {
/* Set the Nimbus look and feel */
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
/* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
* For details see https://docs.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
*/
try {
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(Main.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(Main.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(Main.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(Main.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
//</editor-fold>

/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {

public void run() {
new Main().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JButton HTbtn;
private javax.swing.JTextField NombreTfd;
private javax.swing.JButton TTCBtn;
private javax.swing.JLabel TotalLbl;
private javax.swing.JTextField TvaTfd;
private javax.swing.JLabel jLabel3;
private javax.swing.JPanel jPanel1;
// End of variables declaration
}