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JButton won't show text

This class represents the button panel of a UI I have created, the second JButton named 'btnNext' doesn't display text however the first JButton does, why is this?
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import javax.swing.AbstractAction;
public class ButtonPanel extends JPanel {
private MainPanel mainPanel;
// Buttons
private JButton btnRunTheAlgorithm = new JButton("Run the Algorithm");
public static JButton btnNext = new JButton("Next Step");
public ButtonPanel(MainPanel mainPanel) {
this.mainPanel = mainPanel;
this.setLayout(new FlowLayout());
this.add(btnRunTheAlgorithm);
this.add(btnNext);
this.btnRunTheAlgorithm.addActionListener(e -> {
Algorithm main = new Algorithm(mainPanel);
main.Run();
});
this.btnNext.setAction(new AbstractAction() {
public void actionPerformed(ActionEvent ae) {
synchronized (btnNext) {
btnNext.notify();
}
}
});
}
}
The buttons displays to the panel as on the image below:
Buttons:
I'm also not sure the AbstractAction works, so I suppose that could be the cause of the text not displaying but I have no idea why if that is the case.

In a java Jframe can I add/remove a Jlabel from view using a checkbox?

Im making an application that lets me perform hashes, at the top I want to have a group of check boxes basically saying the four different hash types I have. When the check boxes are selected I want the labels to appear showing the hashed entered text.
I've attached an image to hopefully make it easier to understand what I mean. The reason I'm doing this is so that when the final program is made with almost 10 rows of text boxes and labels it can be reduced only to show the ones that the user wishes to see.This hopefully should explain what I mean.
I've been able to get it so the checkboxes make it visible or not visible but that also then just leaves a blank space where one row of labels used to be rather than moving everything up a row
I've now added my coding so people can see how I'm doing it currently and help define where needs to be modified
import java.awt.*;
import java.awt.event.*;
import java.security.*;
import javax.swing.*;
public class Hasher extends JFrame implements ActionListener {
String UserInput;
private JTextField textInputField;
private static JLabel MD5Hashed,MD5Label;
private static JCheckBox MD5Check, SHA1Check, SHA256Check, FileCheck;
private JFrame contentPane;
public Hasher() {
this.setTitle("Hasher");
Container contentPane = this.getContentPane();
contentPane.setLayout(new GridLayout(0,1) );
contentPane.setBackground(new Color(88,148,202));
//CheckBoxes
JPanel mainPanel = new JPanel();
mainPanel.setLayout(new BorderLayout());
JPanel checkBoxPanel = new JPanel();
MD5Check = new JCheckBox("MD5");
MD5Check.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
boolean Visible = MD5Check.isSelected();
MD5Hashed.setVisible(Visible);
MD5Label.setVisible(Visible);
}
});
checkBoxPanel.add(MD5Check);
SHA1Check = new JCheckBox("SHA-1");
checkBoxPanel.add(SHA1Check);
SHA256Check = new JCheckBox("SHA-256");
checkBoxPanel.add(SHA256Check);
FileCheck = new JCheckBox("File Hashing");
checkBoxPanel.add(FileCheck);
mainPanel.add(checkBoxPanel);
contentPane.add(mainPanel);
//Entered data to perform hash on
contentPane.add(new JLabel (" Enter text to hash"));
textInputField = new JTextField();
//HashingProcess inputListener = new HashingProcess( );
//textInputField.addActionListener(inputListener);
contentPane.add( textInputField);
//MD5 hash is completed
MD5Label = new JLabel( " Using MD5 the hash is: " );
contentPane.add( MD5Label);
MD5Hashed = new JLabel( "??") ;
contentPane.add( MD5Hashed );
MD5Hashed.setVisible(false);
MD5Label.setVisible(false);
}
public static void main(String[] args) {
Hasher theWindow = new Hasher( );
theWindow.setSize(400, 400 );
theWindow.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
theWindow.setVisible(true);
}
}

You have two frames...
public class Hasher extends JFrame implements ActionListener {
//...
private JFrame contentPane;
//..
This immediately raises the question, which one is actually on the screen and which one are you actually interacting with? While this might not be directly related to your problem, it is confusing.
As a general rule of thumb, don't extend from top level containers like JFrame, it locks you into a single use case and can cause no end of confusion. Instead, start with a JPanel and add it to an instance of JFrame or any other container you like.
The "main probable" problem is, Swing is lazy. It won't update the UI until you tell it or the UI is resized.
When adding and removing components, you need to call revalidate and repaint on the container to trigger an update - this is what's actually going wrong in your code, you're referencing contentPane, by that is private JFrame contentPane; and not the contentPane of the JFrame from which Hasher extends ... see, confusion.
Happening dug around your code a bit, it's obvious that you have a lot of repeated operations going on, the only core difference is the algorithm used to hash the text.
So, with that in mind, we can create some basic classes to do most of the work, for example...
public class HashPane extends JPanel {
private JLabel hashedLabel;
private JLabel promptLabel;
private HashAlgorithim algorithim;
public HashPane(String labelText, HashAlgorithim algorithim) {
setOpaque(false);
this.algorithim = algorithim;
setLayout(new FlowLayout(FlowLayout.LEFT));
promptLabel = new JLabel(labelText);
add(promptLabel);
hashedLabel = new JLabel("??");
add(hashedLabel);
}
public void setText(String text) {
hashedLabel.setText(algorithim.generateHash(text));
}
}
This is just two labels, which show a prompt and a result. The result is generated via a plug algorithm which is used to generate the hash for the supplied text
The algorithm itself is just a interface which defines the basic contract...
public interface HashAlgorithm {
public String generateHash(String from);
}
You would then need to create an implementation of each algorithm you wanted to use
Now, making a panel visible/invisible simply becomes a matter of associating a JCheckBox with a HashPane which can be achieved through a simple Map...
public class Hasher extends JPanel {
//...
private Map<JCheckBox, HashPane> mapPanes;
public Hasher() {
//...
HashPane md5Pane = new HashPane("MD5 hash = ", new NotAMD5Alorithim());
//...
HashPane sha1Pane = new HashPane("SHA-1 hash = ", new NotAMSHA1Alorithim());
//..
mapPanes = new HashMap<>(25);
mapPanes.put(MD5Check, md5Pane);
mapPanes.put(SHA1Check, sha1Pane);
//...
You can then use a single ActionListener to manage all the JCheckBoxs
public class Hasher extends JPanel {
//...
private Map<JCheckBox, HashPane> mapPanes;
public Hasher() {
//...
ActionHandler listener = new ActionHandler();
for (Entry<JCheckBox, HashPane> entry : mapPanes.entrySet()) {
entry.getKey().addActionListener(listener);
entry.getValue().setVisible(false);
}
}
protected class ActionHandler implements ActionListener {
#Override
public void actionPerformed(ActionEvent e) {
JCheckBox cb = (JCheckBox) e.getSource();
HashPane hashPane = mapPanes.get(cb);
hashPane.setVisible(cb.isSelected());
revalidate();
repaint();
}
}
And because I pretty much butchered your code...
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.FlowLayout;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;
import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class Hasher extends JPanel {
String UserInput;
private JTextField textInputField;
private static JCheckBox MD5Check, SHA1Check, SHA256Check, FileCheck;
private Map<JCheckBox, HashPane> mapPanes;
public Hasher() {
setLayout(new BorderLayout());
setBackground(new Color(88, 148, 202));
//CheckBoxes
JPanel mainPanel = new JPanel();
mainPanel.setLayout(new BorderLayout());
JPanel checkBoxPanel = new JPanel();
MD5Check = new JCheckBox("MD5");
checkBoxPanel.add(MD5Check);
SHA1Check = new JCheckBox("SHA-1");
checkBoxPanel.add(SHA1Check);
SHA256Check = new JCheckBox("SHA-256");
checkBoxPanel.add(SHA256Check);
FileCheck = new JCheckBox("File Hashing");
checkBoxPanel.add(FileCheck);
mainPanel.add(checkBoxPanel);
add(mainPanel, BorderLayout.NORTH);
JPanel centerPane = new JPanel(new BorderLayout());
centerPane.setOpaque(false);
JPanel inputPane = new JPanel(new FlowLayout(FlowLayout.LEFT));
inputPane.setOpaque(false);
//Entered data to perform hash on
inputPane.add(new JLabel("Enter text to hash: "));
textInputField = new JTextField(20);
inputPane.add(textInputField);
centerPane.add(inputPane, BorderLayout.NORTH);
JPanel output = new JPanel(new GridBagLayout());
output.setOpaque(false);
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridx = 0;
gbc.gridy = 0;
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.weightx = 1;
gbc.gridwidth = GridBagConstraints.REMAINDER;
HashPane md5Pane = new HashPane("MD5 hash = ", new NotAMD5Alorithim());
output.add(md5Pane, gbc);
gbc.gridx = 0;
gbc.gridy++;
HashPane sha1Pane = new HashPane("SHA-1 hash = ", new NotAMSHA1Alorithim());
output.add(sha1Pane, gbc);
// last pane
gbc.gridy++;
gbc.weighty = 1;
output.add(new JLabel(), gbc);
centerPane.add(output);
add(centerPane);
mapPanes = new HashMap<>(25);
mapPanes.put(MD5Check, md5Pane);
mapPanes.put(SHA1Check, sha1Pane);
//...
ActionHandler listener = new ActionHandler();
for (Entry<JCheckBox, HashPane> entry : mapPanes.entrySet()) {
entry.getKey().addActionListener(listener);
entry.getValue().setVisible(false);
}
}
protected class ActionHandler implements ActionListener {
#Override
public void actionPerformed(ActionEvent e) {
JCheckBox cb = (JCheckBox) e.getSource();
HashPane hashPane = mapPanes.get(cb);
hashPane.setVisible(cb.isSelected());
revalidate();
repaint();
}
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new Hasher());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public interface HashAlgorithm {
public String generateHash(String from);
}
public class NotAMD5Alorithim implements HashAlgorithm {
#Override
public String generateHash(String from) {
return "bananas";
}
}
public class NotAMSHA1Alorithim implements HashAlgorithm {
#Override
public String generateHash(String from) {
return "bananas";
}
}
public class HashPane extends JPanel {
private JLabel hashedLabel;
private JLabel promptLabel;
private HashAlgorithm algorithim;
public HashPane(String labelText, HashAlgorithm algorithim) {
setOpaque(false);
this.algorithim = algorithim;
setLayout(new FlowLayout(FlowLayout.LEFT));
promptLabel = new JLabel(labelText);
add(promptLabel);
hashedLabel = new JLabel("??");
add(hashedLabel);
}
public void setText(String text) {
hashedLabel.setText(algorithim.generateHash(text));
}
}
}
Having said all that, I might be tempted to have the JCheckBox in the HashPane and has the HashPane always visible and simply disable the output text ... or simply not bother and always have all the algorithms available all the time

you need to handle Events for all check-box while check/uncheck,
public void actionPerformed(ActionEvent actionEvent) {
if(all check-box un-checked){
// someLable.setVisible(false);
}else if(MD5 checked){
// peform operation based upon MD5
// someLable.setVisible(true);
}
// likewise for all others
}

Change
public void actionPerformed(ActionEvent e) {
boolean Visible = MD5Check.isSelected();
MD5Hashed.setVisible(Visible);
MD5Label.setVisible(Visible);
}
to:
public void actionPerformed(ActionEvent e) {
boolean Visible = MD5Check.isSelected();
MD5Hashed.setVisible(Visible);
MD5Label.setVisible(Visible);
contentPane.validate();
contentPane.repaint();
}
If You want to remove MD5Hashed and MD5Label then something like this:
{
if(MD5Check.isSelected()){
MD5Hashed.remove();
MD5Label.remove();
}
else{
contentPane.add( MD5Label);
contentPane.add( MD5Hashed );
}
contentPane.validate();
contentPane.repaint();
}

TextGUI for chat application.getText() returns null

For one reason getText() returns null.For example:
somebody:hi!
appears as
null:hi!
I have a button which you have to press in order to change the name,but it still returns null as if nothing is written in the JTextField.If I dont' put the button and just use:
username=getText();
it appears as :
:hi!
Here is my code(yes I agree the layout is awful,but currently I am trying just to make it work):
import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
import java.io.IOException;
import java.net.Socket;
import java.util.Scanner;
import java.util.logging.Level;
import java.util.logging.Logger;
public class TextClient extends JFrame{
public JPanel mypanel=new JPanel(new GridBagLayout());
public static JButton send=new JButton("Send");
public static JButton changename=new JButton("Change name");
public static JTextField textf=new JTextField(10);
public static JTextField textname=new JTextField(10);
public static JLabel username=new JLabel("Name:");
public static JTextArea texta=new JTextArea(20,20);
public static JScrollPane jsp=new JScrollPane(texta);
public String user;
public TextClient() throws IOException
{
add(mypanel);
GridBagConstraints c1=new GridBagConstraints();
c1.anchor=GridBagConstraints.SOUTH;
c1.gridx=3;
c1.gridy=1;
mypanel.add(textf,c1);
GridBagConstraints c2=new GridBagConstraints();
c2.gridx=2;
c2.gridy=2;
mypanel.add(jsp,c2);
GridBagConstraints c3=new GridBagConstraints();
c3.gridx=2;
c3.gridy=0;
mypanel.add(send,c3);
GridBagConstraints c4=new GridBagConstraints();
c4.gridx=0;
c4.gridy=0;
mypanel.add(username,c4);
GridBagConstraints c5=new GridBagConstraints();
c5.gridx=1;
c5.gridy=0;
mypanel.add(textname,c5);
GridBagConstraints c6=new GridBagConstraints();
c6.gridx=2;
c6.gridy=1;
mypanel.add(changename,c6);
setVisible(true);
setSize(500,500);
setLocationRelativeTo(null);
setResizable(false);
Socket socket=new Socket("localhost",9000);
changename.addActionListener(new ActionListener(){
#Override
public void actionPerformed(ActionEvent ev)
{
user=textname.getText();
}
});
ClientPeer cp=new ClientPeer(user,socket);
String message=textf.getText();
cp.start();
send.addActionListener(new ActionListener(){
#Override
public void actionPerformed(ActionEvent ev)
{
try {
String sendit=textf.getText();
cp.sendMessage(sendit);
textf.setText("");
} catch (IOException ex) {
Logger.getLogger(TextClient.class.getName()).log(Level.SEVERE, null, ex);
}
}
});
}
public static void main(String [] args)
{
try {
new TextClient();
} catch (IOException ex) {
Logger.getLogger(TextClient.class.getName()).log(Level.SEVERE, null, ex);
}
}
}

Your mixing up objects and variables, and making one call at the wrong time.
Here:
ClientPeer cp=new ClientPeer(user,socket);
String message=textf.getText();
You call getText() in a constructor and not in an ActionListener, meaning you're making this call before the textf JTextField has even been rendered in a GUI and long before the user has had a chance to fill it.
Here:
#Override
public void actionPerformed(ActionEvent ev)
{
user=textname.getText();
}
You change the state of the user field inside of an ActionListener, but unfortunately you use the user varable in the first code that I have shown, again before the field has been rendered and before the user has interacted with it.
I suggest that you put more of your code, including the code that uses the user variable inside your ActionListener code, so that the variable actually holds relevant information.
Other recommendations:
None of your fields should be declared static. If you feel that they must be static to fix an error, then you're fixing the error backwards. The correct fix is to create code that does not require static fields (with some exceptions of course, but none that apply in your current case).
Here's a simplified version of your code, to show you what I mean:
import javax.swing.*;
import java.awt.event.*;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
public class TextClient extends JFrame {
public JPanel mypanel = new JPanel();
public JButton send = new JButton("Send");
public JButton changename = new JButton("Change name");
public JTextField textf = new JTextField(10);
public JTextField textname = new JTextField(10);
public JLabel username = new JLabel("Name:");
public String user;
public TextClient() throws IOException {
add(mypanel);
mypanel.add(textf);
mypanel.add(send);
mypanel.add(username);
mypanel.add(textname);
mypanel.add(changename);
setDefaultCloseOperation(DISPOSE_ON_CLOSE);
pack();
setVisible(true);
setLocationRelativeTo(null);
changename.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent ev) {
user = textname.getText();
System.out.println("user in action listener: " + user);
}
});
// you're trying to use user here!
System.out.println("user outside of action "
+ "listener where you try to use it: " + user); // !!
send.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent ev) {
String sendit = textf.getText();
System.out.println("sendit: " + sendit);
}
});
}
public static void main(String[] args) {
try {
new TextClient();
} catch (IOException ex) {
Logger.getLogger(TextClient.class.getName()).log(Level.SEVERE, null,
ex);
}
}
}

how to make JButton show a list of JButtons with just few items

Hey Guys my problem is when I place the mouse on a JButton in my JFrame, I want it to show a list of JButtons on its left.
I don't known how to do that really I feel like I'm blocked and I cant make any progress in my project.
I'd would be grateful if you could help me and thanks in advance.

Can you create the list of buttons in a JPanel, add it to your JFrame and then call myPanel.setVisible(false). When you click your button then call myPanel.setVisible(true)?
As for ensuring that myPanel is positioned correctly you will want to use a Layout Manager
Or is there a more complex behaviour you want?

A basic option would be to use a MouseListener and a CardLayout. The MouseListener would be used to determine when the mouse cursor enters/exists a given component and the CardLayout would be used to display the appropriate sub component for each "menu" element.
I have to say, JButton would be me last choice for the "menu" item, in most cases, a JLabel would be preferred or even perhaps using a JMenu, which can can have sub menus, which can be displayed automatically might be a better choice, or even a JComboBox....
import java.awt.BorderLayout;
import java.awt.CardLayout;
import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class ShowStuff {
public static void main(String[] args) {
new ShowStuff();
}
public ShowStuff() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
MenuPane menu = new MenuPane();
menu.addMenu("Fruit", new FruitPane());
menu.addMenu("Meat", new MeatPane());
menu.addMenu("Dairy", new DairyPane());
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(menu);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class MenuPane extends JPanel {
private JPanel subMenu;
private JPanel menu;
private CardLayout cardLayout;
private MouseListener mouseHandler;
public MenuPane() {
setLayout(new BorderLayout());
cardLayout = new CardLayout();
subMenu = new JPanel(cardLayout);
menu = new JPanel(new GridBagLayout());
add(subMenu);
add(menu, BorderLayout.WEST);
subMenu.add(new JPanel(), "BLANK");
mouseHandler = new MouseAdapter() {
#Override
public void mouseEntered(MouseEvent e) {
if (e.getSource() instanceof JButton) {
JButton btn = (JButton) e.getSource();
cardLayout.show(subMenu, btn.getText());
}
}
#Override
public void mouseExited(MouseEvent e) {
cardLayout.show(subMenu, "BLANK");
}
};
}
public void addMenu(String name, JPanel subMenuPane) {
JButton button = new JButton(name);
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridwidth = GridBagConstraints.REMAINDER;
menu.add(button, gbc);
subMenu.add(subMenuPane, name);
button.addMouseListener(mouseHandler);
}
}
public abstract class ButtonPane extends JPanel {
private int gridy = 0;
public ButtonPane() {
setLayout(new GridBagLayout());
}
protected void addButton(String name) {
JButton btn = new JButton(name);
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridx = 0;
gbc.gridy = gridy++;
gbc.fill = GridBagConstraints.HORIZONTAL;
add(btn, gbc);
}
}
public class FruitPane extends ButtonPane {
public FruitPane() {
addButton("Banana");
addButton("Grapes");
addButton("Apples");
addButton("Tomatoes");
}
}
public class MeatPane extends ButtonPane {
public MeatPane() {
addButton("Lamb");
addButton("Beef");
addButton("Pork");
addButton("Mince");
}
}
public class DairyPane extends ButtonPane {
public DairyPane() {
addButton("Milk");
addButton("Cream");
addButton("Cheese");
addButton("Yoghurt");
}
}
}

How do I get user input from a JTextField?

I am attempting a very simple form designed to take user input into a JTextField and show that same input via a pop up dialog.
I can hardcode the JTextField to have a preset number using setText(). If I do this, my program works flawlessly.
However, when I leave the field blank and try getText() to show the text in the pop up dialog, I either get an empty pop up frame, or I get an 'empty string' exception (I am attempting to parse String to Double.)
package buttontest;
import java.awt.*;
import java.awt.event.ActionListener;
import java.awt.event.ComponentEvent;
import javax.swing.*;
import java.awt.event.ActionEvent;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
public class ButtonTest
{
public static void main(String[] args)
{
ButtonFrame frame = new ButtonFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}
class ButtonFrame extends JFrame
{
#SuppressWarnings("LeakingThisInConstructor")
public ButtonFrame()
{
setTitle("SunStream Loan Calculator v2.0");
setSize(900,900);
ButtonPanel panel = new ButtonPanel();
panel.add(new JLabel("Enter your loan amount:"));
loanAmt = new JTextField(40);
panel.add(loanAmt);
add(panel,BorderLayout.CENTER);
}
public JTextField loanAmt;
class ButtonPanel extends JPanel implements ActionListener
{
private Component frame;
public ButtonPanel()
{
final JButton b2 = new JButton("Calculate");
add(b2, BorderLayout.SOUTH);
b2.setActionCommand("calculate");
b2.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e)
{
ButtonFrame bf = new ButtonFrame();
if("calculate".equals(e.getActionCommand()))
{
JOptionPane.showMessageDialog(frame, bf.loanAmt.getText());
}
}
});
}
#Override
public void actionPerformed(ActionEvent ae) {
throw new UnsupportedOperationException("Not supported yet.");
}
}
}
Any help would be greatly appreciated. I am researching using a KeyListener or KeyEvent but I don't quite understand it well enough.

You're creating a "shadow" ButtonFrame variable inside of the b2's ActionListener. Yes the bf variable refers to a ButtonFrame object which is of the same class as the displayed ButtonFrame object, but it refers to a completely distinct and non-visualized object. The key to a solution is to get the text from the ButtonFrame object that is actually displayed, and this can be obtained from within an inner class via the ButtonFrame.this construct:
b2.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
//!! ButtonFrame bf = new ButtonFrame();
if ("calculate".equals(e.getActionCommand())) {
//!! note use of ButtonFrame.this:
JOptionPane.showMessageDialog(frame, ButtonFrame.this.loanAmt.getText());
}
}
});
Next consider using public getters rather than accessing fields such as the JTextField directly. This reduces the chances of the code causing side effects, such as changing the properties of the JTextField object inadvertently.
For instance (changes denoted by //!! comment):
import java.awt.*;
import java.awt.event.ActionListener;
import javax.swing.*;
import java.awt.event.ActionEvent;
public class ButtonTest {
public static void main(String[] args) {
ButtonFrame frame = new ButtonFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}
class ButtonFrame extends JFrame {
private JTextField loanAmt; // !! Make field private
#SuppressWarnings("LeakingThisInConstructor")
public ButtonFrame() {
setTitle("SunStream Loan Calculator v2.0");
setSize(900, 900);
ButtonPanel panel = new ButtonPanel();
panel.add(new JLabel("Enter your loan amount:"));
loanAmt = new JTextField(40);
panel.add(loanAmt);
add(panel, BorderLayout.CENTER);
}
// !! create a public method to get JTextField's text
// !! without exposing the JTextField itself.
public String getLoanAmtText() {
return loanAmt.getText();
}
class ButtonPanel extends JPanel implements ActionListener {
private Component frame;
public ButtonPanel() {
final JButton b2 = new JButton("Calculate");
add(b2, BorderLayout.SOUTH);
b2.setActionCommand("calculate");
b2.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
// !! ButtonFrame bf = new ButtonFrame();
if ("calculate".equals(e.getActionCommand())) {
//!! call public method on ButtonFrame object
JOptionPane.showMessageDialog(frame,
ButtonFrame.this.getLoanAmtText());
}
}
});
}
#Override
public void actionPerformed(ActionEvent ae) {
throw new UnsupportedOperationException("Not supported yet.");
}
}
}

The only way you can access your loanAmt is through ButtonPanel itself. Because you add loanAmt to this button right ?
So, if you want access loanAmt. You must get all component on this button panel. This is my psudeo code howto accessing your loanAmt from ButtonPanel class.
b2.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
ButtonFrame bf = new ButtonFrame();
if("calculate".equals(e.getActionCommand())) {
// Get all component
java.awt.Component[] componentList = this.getComponents();
JTextField txtField;
String value;
for (int i = 0; i < componentList.length; i++) {
if (componentList[i].getClass().getName().equals("javax.swing.JTextField")) {
txtField = (JTextField) componentList[i];
value = textField.getText();
}
}
if (value != null) JOptionPane.showMessageDialog(frame, value);
}
}
});