#MainForm.form

<?xml version="1.0" encoding="UTF-8" ?>

<Form version="1.3" maxVersion="1.9" type="org.netbeans.modules.form.forminfo.JFrameFormInfo">
  <Properties>
    <Property name="defaultCloseOperation" type="int" value="3"/>
  </Properties>
  <SyntheticProperties>
    <SyntheticProperty name="formSizePolicy" type="int" value="1"/>
    <SyntheticProperty name="generateCenter" type="boolean" value="false"/>
  </SyntheticProperties>
  <AuxValues>
    <AuxValue name="FormSettings_autoResourcing" type="java.lang.Integer" value="0"/>
    <AuxValue name="FormSettings_autoSetComponentName" type="java.lang.Boolean" value="false"/>
    <AuxValue name="FormSettings_generateFQN" type="java.lang.Boolean" value="true"/>
    <AuxValue name="FormSettings_generateMnemonicsCode" type="java.lang.Boolean" value="false"/>
    <AuxValue name="FormSettings_i18nAutoMode" type="java.lang.Boolean" value="false"/>
    <AuxValue name="FormSettings_layoutCodeTarget" type="java.lang.Integer" value="1"/>
    <AuxValue name="FormSettings_listenerGenerationStyle" type="java.lang.Integer" value="0"/>
    <AuxValue name="FormSettings_variablesLocal" type="java.lang.Boolean" value="false"/>
    <AuxValue name="FormSettings_variablesModifier" type="java.lang.Integer" value="2"/>
  </AuxValues>

  <Layout>
    <DimensionLayout dim="0">
      <Group type="103" groupAlignment="0" attributes="0">
          <Group type="102" alignment="0" attributes="0">
              <EmptySpace min="-2" pref="28" max="-2" attributes="0"/>
              <Group type="103" groupAlignment="1" attributes="0">
                  <Group type="102" attributes="0">
                      <Component id="labelEmail" min="-2" max="-2" attributes="0"/>
                      <EmptySpace min="-2" pref="43" max="-2" attributes="0"/>
                      <Component id="jTextField2" min="-2" pref="323" max="-2" attributes="0"/>
                  </Group>
                  <Group type="102" attributes="0">
                      <Component id="labelFullname" min="-2" max="-2" attributes="0"/>
                      <EmptySpace min="-2" pref="43" max="-2" attributes="0"/>
                      <Component id="jTextField1" min="-2" pref="323" max="-2" attributes="0"/>
                  </Group>
                  <Group type="102" alignment="1" attributes="0">
                      <Component id="labelAddress" min="-2" max="-2" attributes="0"/>
                      <EmptySpace min="-2" pref="43" max="-2" attributes="0"/>
                      <Group type="103" groupAlignment="0" attributes="0">
                          <Group type="102" attributes="0">
                              <Component id="jButton1" min="-2" max="-2" attributes="0"/>
                              <EmptySpace type="separate" max="-2" attributes="0"/>
                              <Component id="jButton2" min="-2" max="-2" attributes="0"/>
                          </Group>
                          <Component id="jTextField3" min="-2" pref="323" max="-2" attributes="0"/>
                      </Group>
                  </Group>
              </Group>
              <EmptySpace pref="38" max="32767" attributes="0"/>
          </Group>
      </Group>
    </DimensionLayout>
    <DimensionLayout dim="1">
      <Group type="103" groupAlignment="0" attributes="0">
          <Group type="102" alignment="0" attributes="0">
              <EmptySpace min="-2" pref="28" max="-2" attributes="0"/>
              <Group type="103" groupAlignment="3" attributes="0">
                  <Component id="labelFullname" alignment="3" min="-2" max="-2" attributes="0"/>
                  <Component id="jTextField1" alignment="3" min="-2" max="-2" attributes="0"/>
              </Group>
              <EmptySpace type="separate" max="-2" attributes="0"/>
              <Group type="103" groupAlignment="3" attributes="0">
                  <Component id="labelEmail" alignment="3" min="-2" max="-2" attributes="0"/>
                  <Component id="jTextField2" alignment="3" min="-2" max="-2" attributes="0"/>
              </Group>
              <EmptySpace type="separate" max="-2" attributes="0"/>
              <Group type="103" groupAlignment="3" attributes="0">
                  <Component id="labelAddress" alignment="3" min="-2" max="-2" attributes="0"/>
                  <Component id="jTextField3" alignment="3" min="-2" max="-2" attributes="0"/>
              </Group>
              <EmptySpace min="-2" pref="26" max="-2" attributes="0"/>
              <Group type="103" groupAlignment="3" attributes="0">
                  <Component id="jButton1" alignment="3" min="-2" max="-2" attributes="0"/>
                  <Component id="jButton2" alignment="3" min="-2" max="-2" attributes="0"/>
              </Group>
              <EmptySpace pref="20" max="32767" attributes="0"/>
          </Group>
      </Group>
    </DimensionLayout>
  </Layout>
  <SubComponents>
    <Component class="javax.swing.JLabel" name="labelFullname">
      <Properties>
        <Property name="text" type="java.lang.String" value="Ho &amp; Ten: "/>
      </Properties>
    </Component>
    <Component class="javax.swing.JTextField" name="jTextField1">
    </Component>
    <Component class="javax.swing.JLabel" name="labelEmail">
      <Properties>
        <Property name="text" type="java.lang.String" value="Email:"/>
      </Properties>
    </Component>
    <Component class="javax.swing.JTextField" name="jTextField2">
    </Component>
    <Component class="javax.swing.JLabel" name="labelAddress">
      <Properties>
        <Property name="text" type="java.lang.String" value="Dia Chi:"/>
      </Properties>
    </Component>
    <Component class="javax.swing.JTextField" name="jTextField3">
    </Component>
    <Component class="javax.swing.JButton" name="jButton1">
      <Properties>
        <Property name="text" type="java.lang.String" value="Vietnam"/>
      </Properties>
      <Events>
        <EventHandler event="actionPerformed" listener="java.awt.event.ActionListener" parameters="java.awt.event.ActionEvent" handler="jButton1ActionPerformed"/>
      </Events>
    </Component>
    <Component class="javax.swing.JButton" name="jButton2">
      <Properties>
        <Property name="text" type="java.lang.String" value="English"/>
      </Properties>
      <Events>
        <EventHandler event="actionPerformed" listener="java.awt.event.ActionListener" parameters="java.awt.event.ActionEvent" handler="jButton2ActionPerformed"/>
      </Events>
    </Component>
  </SubComponents>
</Form>

#MainForm.java

/*
 * Click nbfs://nbhost/SystemFileSystem/Templates/Licenses/license-default.txt to change this license
 * Click nbfs://nbhost/SystemFileSystem/Templates/GUIForms/JFrame.java to edit this template
 */
package com.gokisoft.lesson07;

import java.util.Locale;
import java.util.ResourceBundle;

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

    /**
     * Creates new form MainForm
     */
    public MainForm() {
        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">//GEN-BEGIN:initComponents
    private void initComponents() {

        labelFullname = new javax.swing.JLabel();
        jTextField1 = new javax.swing.JTextField();
        labelEmail = new javax.swing.JLabel();
        jTextField2 = new javax.swing.JTextField();
        labelAddress = new javax.swing.JLabel();
        jTextField3 = new javax.swing.JTextField();
        jButton1 = new javax.swing.JButton();
        jButton2 = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        labelFullname.setText("Ho & Ten: ");

        labelEmail.setText("Email:");

        labelAddress.setText("Dia Chi:");

        jButton1.setText("Vietnam");
        jButton1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton1ActionPerformed(evt);
            }
        });

        jButton2.setText("English");
        jButton2.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton2ActionPerformed(evt);
            }
        });

        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(28, 28, 28)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                    .addGroup(layout.createSequentialGroup()
                        .addComponent(labelEmail)
                        .addGap(43, 43, 43)
                        .addComponent(jTextField2, javax.swing.GroupLayout.PREFERRED_SIZE, 323, javax.swing.GroupLayout.PREFERRED_SIZE))
                    .addGroup(layout.createSequentialGroup()
                        .addComponent(labelFullname)
                        .addGap(43, 43, 43)
                        .addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, 323, javax.swing.GroupLayout.PREFERRED_SIZE))
                    .addGroup(layout.createSequentialGroup()
                        .addComponent(labelAddress)
                        .addGap(43, 43, 43)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addGroup(layout.createSequentialGroup()
                                .addComponent(jButton1)
                                .addGap(18, 18, 18)
                                .addComponent(jButton2))
                            .addComponent(jTextField3, javax.swing.GroupLayout.PREFERRED_SIZE, 323, javax.swing.GroupLayout.PREFERRED_SIZE))))
                .addContainerGap(38, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(28, 28, 28)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(labelFullname)
                    .addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(18, 18, 18)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(labelEmail)
                    .addComponent(jTextField2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(18, 18, 18)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(labelAddress)
                    .addComponent(jTextField3, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(26, 26, 26)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jButton1)
                    .addComponent(jButton2))
                .addContainerGap(20, Short.MAX_VALUE))
        );

        pack();
    }// </editor-fold>//GEN-END:initComponents

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jButton1ActionPerformed
        // TODO add your handling code here:
        setLocale("vi");
    }//GEN-LAST:event_jButton1ActionPerformed

    private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jButton2ActionPerformed
        // TODO add your handling code here:
        setLocale("en");
    }//GEN-LAST:event_jButton2ActionPerformed

    private void setLocale(String lang) {
        Locale locale;
        
        locale = switch (lang) {
            case "vi" -> new Locale("vi", "VN");
            default -> Locale.getDefault();
        };
        
//        ResourceBundle bundle = ResourceBundle.getBundle("com.gokisoft.lession07.messages", locale);
        ResourceBundle bundle = ResourceBundle.getBundle("messages", locale);
        
        labelFullname.setText(bundle.getString("add_user_fullname"));
        labelEmail.setText(bundle.getString("add_user_email"));
        labelAddress.setText(bundle.getString("add_user_address"));
    }
    
    /**
     * @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 http://download.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(MainForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(MainForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(MainForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(MainForm.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 MainForm().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify//GEN-BEGIN:variables
    private javax.swing.JButton jButton1;
    private javax.swing.JButton jButton2;
    private javax.swing.JTextField jTextField1;
    private javax.swing.JTextField jTextField2;
    private javax.swing.JTextField jTextField3;
    private javax.swing.JLabel labelAddress;
    private javax.swing.JLabel labelEmail;
    private javax.swing.JLabel labelFullname;
    // End of variables declaration//GEN-END:variables
}

#messages.properties

add_user_fullname = Full Name
add_user_address = Address
add_user_email = Email

#messages_vi_VN.properties

add_user_fullname = Ho & Ten
add_user_address = Dia Chi
add_user_email = Email