Develop Reference

Save State of Java GUI

I'm pretty new to creating GUIs in Java, so I'm not sure if this is easy or difficult to do. I'm creating a random name chooser, where the user inputs names and then randomly selects some. I am trying to have it save the names entered after the application is closed, and then placed back when it is reopened. I am not sure the best way to go about this; I've looked around a little bit and read a bit about serialization, but it isn't making a lot of sense. Here's my code from NetBeans so far.
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.*;
import javax.sound.sampled.AudioInputStream;
import javax.sound.sampled.AudioSystem;
import javax.sound.sampled.Clip;
import javax.sound.sampled.LineUnavailableException;
import javax.sound.sampled.UnsupportedAudioFileException;
import javax.swing.DefaultListModel;
import sun.applet.Main;
import sun.audio.*;
public class NameChooser extends javax.swing.JFrame {
private ArrayList <Integer> integers;
private Integer index;
private DefaultListModel dlm;
/**
* Creates new form NameChooser
*/
public NameChooser()
{
initComponents();
integers = new ArrayList <Integer>();
dlm = new DefaultListModel();
}
public Integer generateNum()
{
int pings = 0;
do
{
pings = 0;
int temp = (int)(Math.random() * dlm.getSize());
index = new Integer(temp);
for (int k = 0; k < integers.size(); k++)
{
if ((integers.get(k).compareTo(index)) == 0)
{
pings++;
}
}
}
while (pings != 0);
return index;
}
/**
* 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() {
selectButton = new javax.swing.JButton();
jScrollPane2 = new javax.swing.JScrollPane();
names = new javax.swing.JList<>();
nameField = new javax.swing.JTextField();
resetButton = new javax.swing.JButton();
removeButton = new javax.swing.JButton();
jMenuBar1 = new javax.swing.JMenuBar();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
selectButton.setFont(new java.awt.Font("Dialog", 1, 18)); // NOI18N
selectButton.setText("Choose Name");
selectButton.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
selectButtonActionPerformed(evt);
}
});
names.setFixedCellHeight(30);
names.setFixedCellWidth(200);
names.setLayoutOrientation(javax.swing.JList.VERTICAL_WRAP);
jScrollPane2.setViewportView(names);
nameField.setText("Enter Name Here");
nameField.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
nameFieldActionPerformed(evt);
}
});
resetButton.setText("Reset");
resetButton.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
resetButtonActionPerformed(evt);
}
});
removeButton.setText("Remove");
removeButton.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
removeButtonActionPerformed(evt);
}
});
setJMenuBar(jMenuBar1);
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
.addGroup(layout.createSequentialGroup()
.addGap(349, 349, 349)
.addComponent(selectButton, javax.swing.GroupLayout.PREFERRED_SIZE, 197, javax.swing.GroupLayout.PREFERRED_SIZE)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
.addComponent(resetButton))
.addGroup(layout.createSequentialGroup()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(23, 23, 23)
.addComponent(removeButton)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(nameField, javax.swing.GroupLayout.DEFAULT_SIZE, 117, Short.MAX_VALUE)
.addGap(18, 18, 18)))
.addComponent(jScrollPane2, javax.swing.GroupLayout.PREFERRED_SIZE, 589, javax.swing.GroupLayout.PREFERRED_SIZE)))
.addGap(64, 64, 64))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(119, 119, 119)
.addComponent(nameField, javax.swing.GroupLayout.PREFERRED_SIZE, 28, javax.swing.GroupLayout.PREFERRED_SIZE)
.addGap(26, 26, 26)
.addComponent(removeButton)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
.addComponent(selectButton, javax.swing.GroupLayout.PREFERRED_SIZE, 32, javax.swing.GroupLayout.PREFERRED_SIZE)
.addGap(26, 26, 26))
.addGroup(layout.createSequentialGroup()
.addContainerGap(84, Short.MAX_VALUE)
.addComponent(jScrollPane2, javax.swing.GroupLayout.PREFERRED_SIZE, 418, javax.swing.GroupLayout.PREFERRED_SIZE)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addComponent(resetButton)
.addGap(40, 40, 40))
);
pack();
}// </editor-fold>
private void selectButtonActionPerformed(java.awt.event.ActionEvent evt) {
integers.add(generateNum());
if (integers.size() <= dlm.getSize())
{
int [] indexes = new int [integers.size()];
for (int i = 0; i < indexes.length; i++)
{
indexes[i] = integers.get(i).intValue();
}
try {
// Open an audio input stream.
File soundFile = new File("C:\\Users\\Oskar\\Desktop\\sound.wav");
AudioInputStream audioIn = AudioSystem.getAudioInputStream(soundFile);
// Get a sound clip resource.
Clip clip = AudioSystem.getClip();
// Open audio clip and load samples from the audio input stream.
clip.open(audioIn);
clip.start();
} catch (UnsupportedAudioFileException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (LineUnavailableException e) {
e.printStackTrace();
}
//playSound();
names.setSelectedIndices(indexes);
}
}
private void resetButtonActionPerformed(java.awt.event.ActionEvent evt) {
integers.clear();
int[]indexes = new int[0];
names.setSelectedIndices(indexes);
}
private void nameFieldActionPerformed(java.awt.event.ActionEvent evt) {
//Add Name
int size = nameField.getDocument().getLength();
if (size <= 0)
return;
dlm.addElement(nameField.getText());
nameField.setText("");
names.setModel(dlm);
}
private void removeButtonActionPerformed(java.awt.event.ActionEvent evt) {
if (names.getSelectedIndex() != -1)
{
dlm.remove(names.getSelectedIndex());
}
}
/**
* #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(NameChooser.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(NameChooser.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(NameChooser.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(NameChooser.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 NameChooser().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JMenuBar jMenuBar1;
private javax.swing.JScrollPane jScrollPane2;
private javax.swing.JTextField nameField;
private javax.swing.JList<String> names;
private javax.swing.JButton removeButton;
private javax.swing.JButton resetButton;
private javax.swing.JButton selectButton;
// End of variables declaration
}
Could I just make an array or arraylist containing the entered names, somehow save that to a file, then load that file upon running the program to import the names? Or possibly just save the state of the jList? Any help is appreciated.

It is not possible to serialize the state of a Java GUI, because many GUI objects are not serializable.
The JList class is declared as Serializable, so you may be able to serialize it. (It depends on the types of the elements in the list. They also have to be serializable.)
It is theoretically possible to write code that will traverse a GUI data structures, extract the state that needs to be saved into a serializable data structure, and then serialize it. Then you need code to do the reverse; i.e. rebuild / repopulate the GUI from the saved state. (But I suspect you would be better off dealing with this in a different way; e.g. using a custom "preferences" mechanism implemented using properties files or similar.)
However, your aim is to persist the data that you are displaying and updating in the GUI, it is better to do this at the "model" level. Depending on the nature of the model, and the requirements for handling the data, there are other alternatives to object serialization that are:
more efficient,
more scalable,
more resistant to data loss; e.g. when an application crashes,
more able to cope with evolution of the application, and
able to be accessed from outside of Java.

Have a look at java.util.prefs.Preferences. When your app closes, you can do something like...
public void savePreferences() {
Preferences preferences = Preferences.userNodeForPackage(NameChooser.class);
preferences.put("names", "name1, name2, name3");
}
You'll have to extract the names from JList and convert it to a comma delimited string (use StringBuilder). You should be able to get it using JList.getModel. Then when your app loads...
public void loadPreferences() {
Preferences preferences = Preferences.userNodeForPackage(NameChooser.class);
namesAsString = preferences.get("names", null);
}
String.split the namesAsString and whack it back in your JList. Make sense? You got a NullPointerException because I bet you just copy pasted the code. Here's a more simple example:
package example;
import java.util.Date;
import java.util.prefs.Preferences;
public class Example {
public static void main(String[] args) {
Preferences pref = Preferences.userNodeForPackage(Example.class);
String namesAsString = pref.get("names", "empty");
// on first run, this will be empty because you have not saved anything yet
// on succeeding runs, you should see something like:
// Names in preferences: name1Mon May 07 07:15:46 BST 2018, name2Mon May 07 07:15:46 BST 2018
System.out.println("Names in preferences: " + namesAsString);
// simulating new name every time this is run, hence the date
String name1 = "name1" + new Date();
String name2 = "name2" + new Date();
pref.put("names", name1 + ", " + name2);
}
}

You can make a use of Database if you would like to in order to maintain your state. But seems like, just for tiny thing maintaining a database would be costly.
Rather save them in a flat file .txt file and define your own delimiter.
For example:
Insert each record in a new line.
Each value in a record is separated by a pipe |.
Sample of file data:
First Name | Second Name | Anything
First Name 2 | Second Name 2 | Anything else
Then once your application loads up, check for the existence of this file and then read this file. You will need to create your parser which understands your file syntax. And then populate your GUI as per these data (if any).
Update the file if your application requires so
Another approach would be to Create a java class "State" (normal POJO) and then serialize it and save it in your file. When the application loads up, then deserialize it and use in your application.
The problem is:
Overhead of serializing and de-serializing and storing the file
Ensure when object upgrades then you need to maintain old fields (legacy) else your deserializing won't work (common problem of serialization/deserialization).
Google topic around this for more details.

joystick event in java

I have a java application containing one text-field and I'm using a joystick.
How can I do something in the text-field when a button on the joystick is pressed?
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package op;
import net.java.games.input.Controller;
/**
*
* #author Ahmed
*/
public class Test extends javax.swing.JFrame {
/**
* Creates new form Test
*/
public Test() {
initComponents();
con();
}
private void con(){
JInputJoystick joystick = new JInputJoystick(Controller.Type.STICK);
if( !joystick.isControllerConnected() ){
txt.setText("Not Connected");
}
else
txt.setText(joystick.getControllerType()+" "+joystick.getControllerName()+" Controller Cound!");
if( !joystick.pollController() ) {
txt.setText("Controller disconnected!");
}
// Number of buttons.
}
/**
* 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() {
txt = new javax.swing.JTextField();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
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(70, 70, 70)
.addComponent(txt, javax.swing.GroupLayout.DEFAULT_SIZE, 242, Short.MAX_VALUE)
.addGap(88, 88, 88))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(122, 122, 122)
.addComponent(txt, javax.swing.GroupLayout.PREFERRED_SIZE, 33, javax.swing.GroupLayout.PREFERRED_SIZE)
.addContainerGap(145, Short.MAX_VALUE))
);
pack();
}// </editor-fold>
/**
* #param args the command line arguments
*/
// Variables declaration - do not modify
private javax.swing.JTextField txt;
// End of variables declaration
}

Based on the tutorial project here: https://theuzo007.wordpress.com/2013/10/26/joystick-in-java-with-jinput-v2/ it looks like you have to loop and just check things, so
private void con(){
JInputJoystick joystick = new JInputJoystick(Controller.Type.STICK);
while (joystick.isControllerConnected()) {
// Go trough all components of the controller.
Component[] components = joystick.getComponents();
for(int i=0; i < components.length; i++) {
Component component = components[i];
Identifier componentIdentifier = component.getIdentifier();
// Buttons
if(componentIdentifier.getName().matches("^[0-9]*$")){ // If the component identifier name contains only numbers, then this is a button.
// Is button pressed?
if(component.getPollData() != 0.0f) {
txt.setText("Button got pressed!")
}
}
}
// We have to give processor some rest.
try {
Thread.sleep(25);
} catch (InterruptedException ex) {
Logger.getLogger(JoystickTest.class.getName()).log(Level.SEVERE, null, ex);
}
}
txt.setText("Controller not connected");
}

how to monitor the close event of a JDialog?

I have got a tricky problem. I need to pop a confirm message box for user to decide close or not when someone click the close sign on the right upper corner of the window. But It doesn't work. Whatever you choose in the pop message box , the dialog will always be closed. But the same logic works fine when I create a JFrame.
Below is my code in my netbeans IED.
I just use a WindowAdpter to catch the close event, plz igore the dummy code generated by neatbean.
Thanks.
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
public class TestClosingDialog extends javax.swing.JDialog {
public TestClosingDialog(java.awt.Frame parent, boolean modal) {
super(parent, modal);
initComponents();
this.addWindowListener(new WindowAdapter() {
#Override
public void windowClosing(WindowEvent e) {
int a = JOptionPane.showConfirmDialog(null,"Are you sure you need to close？", "Tip", JOptionPane.YES_NO_OPTION);
if (a == 0) {
System.out.println("yes " + a);
System.exit(0); //close
} else if (a==1) {
System.out.println("no " + a);
}
}
});
}
/**
* 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() {
setDefaultCloseOperation(javax.swing.WindowConstants.DISPOSE_ON_CLOSE);
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 400, Short.MAX_VALUE)
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 300, Short.MAX_VALUE)
);
pack();
}// </editor-fold>
/**
* #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(TestClosingDialog.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(TestClosingDialog.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(TestClosingDialog.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(TestClosingDialog.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
//</editor-fold>
/* Create and display the dialog */
java.awt.EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
TestClosingDialog dialog = new TestClosingDialog(new JFrame(), true);
dialog.setVisible(true);
}
});
}
// Variables declaration - do not modify
// End of variables declaration
}

Change setDefaultCloseOperation(javax.swing.WindowConstants.DISPOSE_ON_CLOSE); to setDefaultCloseOperation(javax.swing.WindowConstants.DO_NOTHING);
This will require you to manually dispose of the dialog. Depending on your needs, you would simply need to change System.exit(0); to dispose();
I would, personally, advise against extending directly from a top level container like JDialog, but that's just me.
I prefer to use, something like, a JPanel that has a helper method that can display an dialog. This method would create the dialog and add the panel to it, for example

how to write answers in textArea GUI from base code

I had some questions earlier regarding this base code which were
solved here but now my issue is that i have to take this code and get
out the result in GUI textArea. What ive done so far is that ive
designed a textArea and a button but now im stuck. I dont know how to
translate that code i used as a base into the GUI and make it possible
to click on the button and display the answers into the textdisplay. I
dont know if i should copy this base code somewhere or do i need to do
totally different thing inside of the GUI? For instance under
jButtonActionPerformed, what do i need to do... im sorry im new to
this and so lost. Ive googled all day but its hard to understand.
Here is the base code :
import java.lang.String;
class Vara {
//Deklarerar variabler
private String name;
private double price;
private int antal;
//tildela konstruktorer för de deklarerade variablerna
public Vara (String name, int antal, double price) {
this.name = name;
this.antal = antal;
this.price = price;
} // slut constructor
public void setName(String name) {
this.name = name; }
public void setPrice (double price) {
this.price = price; }
public void setAntal (int antal) {
this.antal = antal; }
public String getName() {
return this.name;}
public double getPrice() {
return this.price; }
public int getAntal() {
return this.antal; }
}
//testklassen ska stå som en egen klass
class Test {
public static void main(String[] args){
Vara var = new Vara("Banan",5, 12.5);
System.out.println("Namnet är " +var.getName() +" och priset är " +var.getPrice() +" och antalet är "+var.getAntal() );// här slutar system.out
}
}
And here is the beginning of my code in GUI which i havent done anything on so far except creating a textArea and a button.
public class NewJFrame extends javax.swing.JFrame {
/**
* Creates new form NewJFrame
*/
public NewJFrame() {
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() {
jScrollPane1 = new javax.swing.JScrollPane();
jTextArea1 = new javax.swing.JTextArea();
jButton1 = new javax.swing.JButton();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
jTextArea1.setColumns(20);
jTextArea1.setRows(5);
jScrollPane1.setViewportView(jTextArea1);
jButton1.setText("jButton1");
jButton1.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton1ActionPerformed(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()
.addContainerGap(29, Short.MAX_VALUE)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addComponent(jButton1, javax.swing.GroupLayout.PREFERRED_SIZE, 213, javax.swing.GroupLayout.PREFERRED_SIZE)
.addGap(69, 69, 69))
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 361, javax.swing.GroupLayout.PREFERRED_SIZE)
.addContainerGap())))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 231, javax.swing.GroupLayout.PREFERRED_SIZE)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
.addComponent(jButton1, javax.swing.GroupLayout.PREFERRED_SIZE, 30, javax.swing.GroupLayout.PREFERRED_SIZE)
.addContainerGap(17, Short.MAX_VALUE))
);
pack();
}// </editor-fold>
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
txtDisplay.setText(null);
txtDisplay.append(String.valueOf(String)+"\n");
// 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
* 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(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(NewJFrame.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 NewJFrame().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JButton jButton1;
private javax.swing.JScrollPane jScrollPane1;
private javax.swing.JTextArea jTextArea1;
// End of variables declaration
}

in GUI Class make set the modifier to "Public Static" so it can be accessed from other class.
public static javax.swing.JTextArea jTextArea1;
then you can enter Value in this jTextArea1 from other classes. by accessing directly like this
NewJFrame.jTextArea1.append("text to append");

From your question it is not obvious if you want to put in data into your JTextArea or to read the content entered in the JTextArea in order to store it somewhere else. I will answer for both cases.
An elegant way to wire up data and GUI is to insert the data model object (in your case an instance of the class Vara) into a GUI object. E.g. this can be done right at the GUI object creation as shown in the code below. I commented each new line in your code with "// CHANGED: ...".
public class NewJFrame extends javax.swing.JFrame {
// CHANGED: store the model for this GUI
private Vara vara;
/**
* Creates new form NewJFrame
*/
public NewJFrame(Vara vara) { // CHANGED: provide the model for this GUI
this.vara = vara; // CHANGED: store the model for this GUI
initComponents();
// CHANGED: set TextArea content according to the data in the
// provided model object (if this is what you want)
jTextArea1.setText(vara.getName());
}
...
...
...
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
txtDisplay.setText(null);
txtDisplay.append(String.valueOf(String)+"\n");
// CHANGED: read the entered text from the TextArea and store it as the
// new name of the Vara object (if this is what you want to happen when
// the user clicks on the button)
vara.setName(jTextArea1.getText());
}
...
...
...
// Variables declaration - do not modify
private javax.swing.JButton jButton1;
private javax.swing.JScrollPane jScrollPane1;
private javax.swing.JTextArea jTextArea1;
// End of variables declaration
}
Some tips for a better programmer life:
use English everywhere, also in the comments
always name the GUI elements reasonable, e.g. your jButton1 could be btnSave ("btn" stands for Button) and your jTextArea1 could be taVaraName ("ta" stands for TextArea) - this greatly increase readability of your GUI code and makes debugging and maintaining much easier
use Eclipse for Java development, esp. if you want to build GUIs. It comes with a plugin called Eclipse WindowBuilder. This is "a powerful and easy to use bi-directional Java GUI designer", means you can: (1) easily drag-and-drop your GUI elements and get the code automatically generated for you; (2) modify any part of the code and see the drag-and-drop view automatically changing accordingly. It generates much cleaner and often shorter GUI code than the one you posted and lets you modify everything (does not have the "don't modify" parts you have in your code)

How do I get a JComponent to resize after calling `setVisible(true)`?

Our application displays a 2D view of our data (mainly maps) and then allows the user to change to a 3D view. The 2D and 3D views are generated by custom C++ code that is SWIG'ed into our Swing GUI and wrapped within a JComponent. These JComponents are then displayed within another parent JComponent.
Our problem is that when we change from the 2D to the 3D view and then back to the 2D view, when we resize the window the 2D view does not get resized. The resize events don't get sent to the 2D view.
Our application runs under Linux (Fedora 11). We're running Java version 1.6.0_12.
Here is some sample code in which I've replaced the 2D view and 3D view with two 2 JButtons, that produces the same behaviour. Once you go to 3D and then back to 2D, resizing the window does not cause the 2D view to be resized.
/* TestFrame.java
* Compile with: $ javac TestFrame.java
* Run with: $ java TestFrame
*/
import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.event.ComponentEvent;
import java.awt.event.ComponentListener;
import javax.swing.JButton;
public class TestFrame extends javax.swing.JFrame {
private boolean mode2D = true;
private JButton view2D = null;
private JButton view3D = null;
private Container parent = null;
public TestFrame() {
initComponents();
containerPanel.setLayout(new BorderLayout());
view2D = new JButton("2D View");
view2D.addComponentListener(new MyListener("2D VIEW"));
containerPanel.add(view2D);
}
private void changerButtonActionPerformed(java.awt.event.ActionEvent evt) {
if (parent == null) {
parent = view2D.getParent();
}
if (mode2D) {
System.out.println("Going from 2D to 3D");
view2D.setVisible(false);
if (view3D != null) {
view3D.setVisible(true);
} else {
view3D = new JButton("3D View");
view3D.addComponentListener(new MyListener("3D VIEW"));
parent.add(view3D);
}
((JButton) evt.getSource()).setText("Change to 2D");
mode2D = false;
} else {
System.out.println("Going from 3D to 2D");
view3D.setVisible(false);
view2D.setVisible(true);
((JButton) evt.getSource()).setText("Change to 3D");
mode2D = true;
}
}
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new TestFrame().setVisible(true);
}
});
}
private javax.swing.JPanel containerPanel;
private javax.swing.JButton changerButton;
private class MyListener implements ComponentListener {
private String name;
public MyListener(String name) {
this.name = name;
}
#Override
public void componentHidden(ComponentEvent event) {
System.out.println("### [" + name + "] component Hidden");
}
#Override
public void componentResized(ComponentEvent event) {
System.out.println("### [" + name + "] component Resized");
}
#Override
public void componentShown(ComponentEvent event) {
System.out.println("### [" + name + "] component Shown");
}
#Override
public void componentMoved(ComponentEvent event) {
System.out.println("### [" + name + "] component Moved");
}
};
#SuppressWarnings("unchecked")
private void initComponents() {
containerPanel = new javax.swing.JPanel();
changerButton = new javax.swing.JButton();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
containerPanel.setBorder(new javax.swing.border.MatteBorder(null));
javax.swing.GroupLayout containerPanelLayout = new javax.swing.GroupLayout(containerPanel);
containerPanel.setLayout(containerPanelLayout);
containerPanelLayout.setHorizontalGroup(
containerPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 374, Short.MAX_VALUE)
);
containerPanelLayout.setVerticalGroup(
containerPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 239, Short.MAX_VALUE)
);
changerButton.setText("Change to 3D");
changerButton.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
changerButtonActionPerformed(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()
.addContainerGap()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(containerPanel, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
.addComponent(changerButton))
.addContainerGap())
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(containerPanel, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addComponent(changerButton)
.addContainerGap())
);
pack();
}
}
(My apologies for the Netbeans generated GUI code)
I should mention that when we call parent.remove(view2D) and parent.add(view3D) to change the views the X Windows ID of our 3D view changes and we're unable to get our 3D view back. Therefore parent.remove(view2D) and parent.add(view3D) is not really a solution and we have to call setVisible(false) and setVisible(true) on the JComponents that contain our 2D and 3D views in order to hide and show them.
Any help will be greatly appreciated.

Why don't you use a CardLayout to switch from the 2D to 3D component?
CardLayout is exactly done for this kind of purpose in my understanding.
Another benefit would be that it will simplify your code.

After your remove() and add() methods to change the component, you should call:
parent.revalidate(); //To make the layout manager do its work.
parent.repaint(); //This could be necessary, to suggest a repaint of the panel
Javadoc for JComponent#revalidate() :
Supports deferred automatic layout.
Calls invalidate and then adds this
component's validateRoot to a list of
components that need to be validated.
Validation will occur after all
currently pending events have been
dispatched. In other words after this
method is called, the first
validateRoot (if any) found when
walking up the containment hierarchy
of this component will be validated.
By default, JRootPane, JScrollPane,
and JTextField return true from
isValidateRoot.
This method will automatically be
called on this component when a
property value changes such that size,
location, or internal layout of this
component has been affected. This
automatic updating differs from the
AWT because programs generally no
longer need to invoke validate to get
the contents of the GUI to update.

I've found a solution. You need to add/remove the components from the layout manager:
private void changerButtonActionPerformed(java.awt.event.ActionEvent evt) {
if (parent == null) {
parent = view2D.getParent();
}
LayoutManager layoutMgr = parent.getLayout();
if (mode2D) {
System.out.println("Going from 2D to 3D");
view2D.setVisible(false);
layoutMgr.removeLayoutComponent(view2D);
if (view3D != null) {
view3D.setVisible(true);
if (layoutMgr != null && layoutMgr instanceof LayoutManager2) {
((LayoutManager2) layoutMgr).addLayoutComponent(view3D, null);
}
} else {
view3D = new JButton("3D View");
view3D.addComponentListener(new MyListener("3D VIEW"));
parent.add(view3D);
}
((JButton) evt.getSource()).setText("Change to 2D");
mode2D = false;
} else {
System.out.println("Going from 3D to 2D");
view3D.setVisible(false);
layoutMgr.removeLayoutComponent(view3D);
view2D.setVisible(true);
if (layoutMgr != null && layoutMgr instanceof LayoutManager2) {
((LayoutManager2) layoutMgr).addLayoutComponent(view2D, null);
}
((JButton) evt.getSource()).setText("Change to 3D");
mode2D = true;
}
}