Java JFrame not working properly in while loop - java

When I try to run this, I keep getting an empty frame that cannot be closed, and I have to terminate the program from eclipse. I am fairly certain that the problem is a result of the while loop (about 2/3 of the way down the code block), but I haven't been able to figure out a way to fix this
public Draw()
{
super( "Uno");
JMenuBar bar = new JMenuBar(); // create menu bar
JMenu gameMenu = new JMenu( "Play Game" );
JMenu quitMenu = new JMenu( "Quit" ); //Quit Program
bar.add( gameMenu ); // add Add menu to menu bar
bar.add( quitMenu ); // add quit button to menu bar
setJMenuBar( bar ); // set menu bar for this application
window = new JDesktopPane();
add(window);
gameMenu.addMouseListener(
new MouseListener()
{
public void mouseClicked(MouseEvent e)
{
Dimension size = window.getSize();
double height = size.getHeight();
double width = size.getWidth();
JInternalFrame frame = new JInternalFrame("Uno", true, true, true, true );
JFrame input = new JFrame();
input.setTitle(" ");
input.setSize(350, 155);
input.setLayout(new FlowLayout());
input.setLocationRelativeTo(null);
input.setVisible(true);
JLabel label1 = new JLabel("How many total players? (2-10)");
final JTextField text1 = new JTextField(3);
JLabel label2 = new JLabel("How many computer players? *");
final JTextField text2 = new JTextField(3);
JLabel label3 = new JLabel("* Computer players must be <= total number of players");
JButton confirm = new JButton("OK");
label1.setVisible(true);
label2.setVisible(true);
label3.setVisible(true);
text1.setVisible(true);
text2.setVisible(true);
confirm.setVisible(true);
input.add(label1);
input.add(text1);
input.add(label2);
input.add(text2);
input.add(label3);
input.add(confirm);
while(valid == false)
{
confirm.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
String players = text1.getText();
String computers = text2.getText();
int temp1 = Integer.parseInt(players);
System.out.println("Number of players = " + temp1);
int temp2 = Integer.parseInt(computers);
System.out.println("Number of computers = " + temp2);
if (temp1 >= 2 && temp1 <= 10)
if (temp2 <= temp1 && temp2 >= 0)
valid = true;
} //close actionPerformed
}); //close ActionListener
} //close while loop
} //close mouseClicked
} //close mouseListener
} //close Draw
Initially, I was having an issue where it kept infinitely drawing the frame on top of itself because the while loop kept returning false. That issue was solved by removing the components from the while loop, and placing them before it as they are above. Now when I run it, all I get is this: picture
The goal of this program is to make an Uno game, but the first step is to determine the number of players. This is the only way I know how to do this, and this is only the second program I have done with graphics, so I am by no means an expert at Java. I will appreciate any help I can get because I have been stuck for a few days now.

The problem is that you are not giving the event handlers any chance to do their job. Your while loop continually creates event handlers. However, the actionPeformed() method can never be called because the while loop has control of the CPU and the button will not respond to any clicks.
I suggest that you learn a bit more about event handling. You will need to redesign your code in order to get the behavior you wish. Most likely you need to remove the while loop entirely and just create an event handler which will execute code when the button is clicked.
For future reference:
In general, checking equality with a boolean value is unnecessary. The result of == is a bool, but the variable you are checking is already a bool. So use it directly: instead of while (valid == false), you can do while (!valid). If you read the ! as "not", this actually makes a lot of sense.
In this case, the point is moot, since you need to remove the while loop entirely. However, this might be useful information for you some time in the future.

Related

Convert an incrementing/changing String value to existing incremental variable name of JButtons to modify their properties in java

Simplified: How to make String value to call specific existed JButton variable name in java?
I'm trying to make a non-ordinary Tic-Tac-Toe game...
Anyway, what I will post here is not really the whole concept of that. I just want to make it simple: I have 9 square jButtons named (3 by 3) (and maybe allow user to make 4x4, 5x5, 10x10 etc. via settings in future):
[markbox_00_00] / [markbox_00_01] / [markbox_00_02]
[markbox_01_00] / [markbox_01_01] / [markbox_01_02]
[markbox_02_00] / [markbox_02_01] / [markbox_02_02]
[btnSave] / [btnUndoActions]
where the first two digit represent the row and the next two is the column; and a save button (btnSave) and undo button(btnUndoActions).
Each markbox have default spring value of "0", when I click it turns "1"; and when I click "1" it turns "0". When you press undo button it will reset to last save.
Here is some of my simplified line of codes:
private byte markboxColLimit = 3, markboxRowLimit = 3, row, col;
private byte[][] saveNumber = new byte[markboxRowLimit][markboxColLimit];
private String buttonName;
public Astral_TicTacToe() {
initComponents();
/* I want something like this, but using a for loop based on markboxColLimit and
markboxRowLimit as limits */
markbox_00_00.setText("0");
markbox_00_01.setText("0");
markbox_00_02.setText("0");
markbox_01_00.setText("0");
markbox_01_01.setText("0");
markbox_01_02.setText("0");
markbox_02_00.setText("0");
markbox_02_01.setText("0");
markbox_02_02.setText("0");
/* I know the line below is wrong... what I'm trying is to avoid
* repetitiveness by looping and dynamically calling the variable
* name of JButtons, or in other ways...
*/
/* Attempting to make an alternative code from above (trying to make a loop instead) */
for(row = 0; row < markboxRowLimit; row++){
for(col = 0; col < markboxColLimit; col++){
buttonName = "markbox_0" + Byte.toString(row) + "_0" + Byte.toString(col);
buttonName.setText("0");
}
}
}
private void btnUndoActionsActionPerformed(java.awt.event.ActionEvent evt) {
markbox_00_00.setText(Byte.toString(saveNumber[0][0]));
markbox_00_01.setText(Byte.toString(saveNumber[0][1]));
markbox_00_02.setText(Byte.toString(saveNumber[0][2]));
markbox_01_00.setText(Byte.toString(saveNumber[1][0]));
markbox_01_01.setText(Byte.toString(saveNumber[1][1]));
markbox_01_02.setText(Byte.toString(saveNumber[1][2]));
markbox_02_00.setText(Byte.toString(saveNumber[2][0]));
markbox_02_01.setText(Byte.toString(saveNumber[2][1]));
markbox_02_02.setText(Byte.toString(saveNumber[2][2]));
}
private void btnSaveActionPerformed(java.awt.event.ActionEvent evt) {
saveNumber[0][0] = Byte.parseByte(markbox_00_00.getText());
saveNumber[0][1] = Byte.parseByte(markbox_00_01.getText());
saveNumber[0][2] = Byte.parseByte(markbox_00_02.getText());
saveNumber[1][0] = Byte.parseByte(markbox_01_00.getText());
saveNumber[1][1] = Byte.parseByte(markbox_01_01.getText());
saveNumber[1][2] = Byte.parseByte(markbox_01_00.getText());
saveNumber[2][0] = Byte.parseByte(markbox_02_00.getText());
saveNumber[2][1] = Byte.parseByte(markbox_02_01.getText());
saveNumber[2][2] = Byte.parseByte(markbox_02_02.getText());
}
private void markbox_00_00ActionPerformed(java.awt.event.ActionEvent evt) {
if("0".equals(markbox_00_00.getText()))
markbox_00_00.setText("1");
else
markbox_00_00.setText("0");
}
private void markbox_00_01ActionPerformed(java.awt.event.ActionEvent evt) {
if("0".equals(markbox_00_01.getText()))
markbox_00_00.setText("1");
else
markbox_00_00.setText("0");
}
....
private void markbox_02_02ActionPerformed(java.awt.event.ActionEvent evt) {
if("0".equals(markbox_00_00.getText()))
markbox_02_02.setText("1");
else
markbox_02_02.setText("0");
}
In short: how can I make String a specific variable name of JButton for calling/accessing/editing for their properties?
Example:
buttonName = markbox_01_02;
buttonName.setText("2");
is equavalent to markbox_01_02.getText("2");
I really appreciate the help, thank you...
P.S. I use to make JFrame in NetBeans Design (just click and drag the objects in palette window like JPanel, JButton, etc., so I don't type the code manually except making my own logical Method).
You probably need to redo your program and rephrase your question because it's kind of unclear where you're stuck that's why I wrote this answer as a Community Wiki.
The following program creates a GridLayout for the board and add 2 JButtons below it which contain "Save" and "Undo" buttons.
Whenever you press a button it will change it's text to 0 or 1 depending on the previous state of the button, and "Undo" button will undo last clic the same way, if it was 0 it will become 1 and viceversa.
I guess you should read How to write an ActionListener before copy-pasting this example, understand what it says and try to understand how this program works.
The logic to "Save" button is up to you 'cause I'm not sure what you wanna do there and I'm not gonna write all the code for you. This is made only for you to get an idea on how to handle events.
Also, the logic to end the game is left to you for the same reasons as the "Save" button.
I wish I knew how to record my screen in Ubuntu and save as GIF but here's a screenshot on how this program looks like:
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class TicTacToe implements ActionListener {
JFrame frame;
JButton buttons[];
JPanel pane, buttonPane;
boolean pressed[];
JButton save, undo;
int n = -1;
public void actionPerformed(ActionEvent e) {
for (int i = 0; i < buttons.length; i++) {
if(e.getSource() == buttons[i]) {
pressed[i] = !pressed[i];
buttons[i].setText(pressed[i] ? "1" : "0");
n = i;
break;
}
}
}
public TicTacToe () {
frame = new JFrame("Tic Tac Toe Game");
buttons = new JButton[9];
pane = new JPanel(new GridLayout(3, 3));
pressed = new boolean[9];
buttonPane = new JPanel(new FlowLayout());
save = new JButton("Save");
undo = new JButton("Undo");
for (int i = 0; i < buttons.length; i++) {
buttons[i] = new JButton("0");
pressed[i] = false;
}
for (JButton b : buttons) {
b.addActionListener(this);
pane.add(b);
}
undo.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ae) {
if (n == -1) {
return;
}
pressed[n] = !pressed[n];
buttons[n].setText(pressed[n] ? "1" : "0");
}
});
buttonPane.add(save);
buttonPane.add(undo);
frame.add(pane, BorderLayout.PAGE_START);
frame.add(buttonPane, BorderLayout.CENTER);
frame.pack();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
public static void main (String args[]) {
new TicTacToe();
}
}

give JButton multiple options for mouse clicks (Blackjack Game)

I am writing a Blackjack program using JFrame and trying to keep it as simple as possible. My JButton, jbHit works with a single click, however it overwrites the playersHand and playerSide slot with every click. I would like it to work with multiple clicks (3 clicks - since that is the max number of cards you can get after the first two are dealt) options It should count them so to speak so that the array index can record the card image. Here is my ActionListener code that I have so far. I am afraid I am stuck. Should I use some sort of for loop with an int i++?
//Hit Button ActionListener
jbHit.addActionListener( new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
if ( playerValue < 21 ) {
//Draw a card
Card c = deck.drawCard();
playersHand.add(c);
playerSide[2].setIcon( new ImageIcon( c.getFilename() ) );
}
//If playerValue > 21, bust
else if ( playerValue > 21 ) {
//Toggle Buttons
jbDeal.setEnabled(true);
jbHit.setEnabled(false);
jbStand.setEnabled(false);
jbDoubleDown.setEnabled(false);
message = "You bust.";
}
}
});
You could create an array of "action commands" and every time you click the button, the action command changes to the next. If you reach the end, set the index back to zero. Perhaps something like this:
public static void main(String[] args)
{
JFrame frame = new JFrame();
JPanel panel = new JPanel();
JButton button = new JButton("Action");
String[] commands = {"command1", "command2", "command3"};
button.setActionCommand(commands[0]);
button.addActionListener(new ActionListener()
{
#Override
public void actionPerformed(ActionEvent e)
{
JButton btn = (JButton)e.getSource();
String cmd = btn.getActionCommand();
System.out.println("Command: " + cmd);
if(cmd.equals("command1"))
{
btn.setActionCommand(commands[1]);
System.out.println("Command 1 was pressed");
}
else if(cmd.equals("command2"))
{
btn.setActionCommand(commands[2]);
System.out.println("Command 2 was pressed");
}
else if(cmd.equals("command3"))
{
btn.setActionCommand(commands[0]);
System.out.println("Command 3 was pressed");
}
else
System.out.println("Something went wrong!");
}
});
panel.add(button);
frame.add(panel);
frame.setSize(200, 200);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
If you are using Java 7 or later, you can replace the if/else with a Switch statement.
I believe you're looking for a logical flag based on an integer, for example:
if(cardsDealt < 3) {
// DoThings();
} else {
return;
}
Which would require you to do
cardsDealt++;
at the bottom of your button click handle.
If this is not what you're asking, please re-explain the question.
It sounds like you might be a little confused about how jbHit will be called. Realize that it will be called one complete time every time the mouse is clicked. It's not like it inherently knows that it is on the second or third click. Add a class member like int clickCount; that you increment at the appropriate point inside of jbHit. Then you can alter your method's response depending on the value of clickCount.

JButton doesn't appear until clicked

For this program, the JButton doesn't seem to show up unless you click the area where the JButton should be; the JFrame starts up blank. The moment you click the button, the respective code runs and the button finally shows up.
How do I get the buttons to show up upon starting the program?
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
/*
The Amazing BlackJack Advisory Tool by JoshK,HieuV, and AlvinC.
Prepare to be amazed :O
*/
public class BlckJackUI {
//main class, will contain the JFrame of the program, as well as all the buttons.
public static void main(String args[])
{
//Creating the JFrame
JFrame GUI = new JFrame("Blackjack Advisor");
GUI.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
GUI.setSize(1300, 900);
GUI.setContentPane(new JLabel(new ImageIcon("C:\\Users\\Hieu Vo\\Desktop\\Green Background.png")));
GUI.setVisible(true);
// Because each button needs to run through the Math class.
final Math math = new Math();
// The Ace Button:
ImageIcon Ace = new ImageIcon("/Users/computerscience2/Downloads/Ace.jpg");
JButton ace = new JButton(Ace);
ace.setSize(300, 100);
ace.setLocation(100, 100);
ace.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
//Automatically default the the Ace to 11, and if Bust, Ace becomes 1.
if (math.array.playerhandtotal <= 21)
{
math.cardvalue = math.cardvalue + 11;
}
else
{
math.cardvalue = math.cardvalue + 1;
}
math.array.clicktracker++;
math.calcResult();
JOptionPane.showMessageDialog(null,math.array.result);
}
});
GUI.add(ace);
ImageIcon Two = new ImageIcon("/Users/computerscience2/Downloads/2.jpg");
JButton two = new JButton(Two);
two.setSize(300, 100);
two.setLocation(100, 200);
two.addActionListener(new ActionListener ()
{
public void actionPerformed(ActionEvent e)
{
/*
This generally repeats throughout the whole class, and the only
thing different is the changing cardvalue. When a button is pressed,
respective cardvalues are added into the playerhand ArrayList, and
totaled up to form playerhandtotal, which is a major factor in
bringing up the advice.
*/
math.cardvalue = math.cardvalue + 2;
math.array.clicktracker++;
math.calcResult();
JOptionPane.showMessageDialog(null,math.array.result);
}
});
GUI.add(two);
Et cetera, Et cetera... Just a bunch of the same stuff, more buttons coded the same exact way as JButton two, but with different value associated to them.
JButton start = new JButton("Start/Reset");
start.setSize(300, 100);
start.setLocation(500,500);
start.addActionListener(new ActionListener ()
{
public void actionPerformed(ActionEvent e)
{
/*
The start button also acts like a reset button, and the concept is fairly
simple. If we reset all the important values to 0 or "null," then the
program acts as if it was just opened.
*/
Arrays array = new Arrays();
array.playerhand.clear();
array.dealer = 0;
math.array.starttracker++;
math.array.clicktracker = 0;
array.playerhandtotal = 0;
math.cardvalue = 0;
array.result = null;
JOptionPane.showMessageDialog(null,"Please select the card \nthat the dealer is showing :)");
}
});
GUI.add(start);
GUI.setLayout(null);
This is all in the same class, and I understand a layout would be nicer, but perhaps there's a way to fix this issue using what I have now?
The program starts blank because you are calling setVisible before you add components. Call setVisible after you add components (in the end of contructor) and it should work fine.
Also, avoid absolute positioning and call of set|Preferred|Minimum|MaximumSize methods for your components. Learn how to use layout managers.
Write GUI.validate(); after you add all the components to your frame. Any time you add something to a frame you have to validate it like this. Otherwise, you will get the behavior that you have described.
No. The problem is caused by the layout. Before adding anything to a JFrame or a JPanel which you want it to have an absolute position, you have to setLayout(null). Otherwise, you'll have unexpected behaviours all the time. I just figured it out by myself after three hours of experimenting; suddenly, I connected your post with other different subject, and it worked, but this isn't well explained on the Internet yet.

No visual appearing

I am working on a java game for class where we implement a game of nim. I thought that I was nearing completion but when I ran the program, nothing appears. It just says build successful and quits. I never get to see the game or play it. Below is my code for the application.
package Nim;
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class Nim extends JFrame implements ActionListener {
// Number of stickSpace that is needed for the sticks;
int rowspace = 3;
// Buttons for the human to click to take turns playing witht the computer.
private JButton humanMove,
computerMove;
// whatRow = what row the user would like to remove from
// howMany = how many sticks to take from each row
private JComboBox whatRow,
howMany;
// Creates an array of JTextFields with the rowspace as a size.
private JTextField[] stickSpace = new JTextField[rowspace];
// Creates the game;
private Nimgame nimgame;
public void Nim(){
//As requireed, we use a loop to fill the array.
for(int i=0; i<rowspace ;i++){
stickSpace[i] = new JTextField(5);
}
// Creates pulldown menus for the user to select the whatRow s/he
// wants to choose from, and another for howMany s/he wants to take.
whatRow = new JComboBox();
howMany = new JComboBox();
// Add the options to the pulldown menus so the player can choose.
// 0-2 because the array index starts at 0. 1-3 for the amount of sticks.
for(int p=0; p<=3; p++){
if(p<3){
whatRow.addItem(p);
}
if(p>0){
howMany.addItem(p);
}
}
// Adds the text "Human Turn" and "CPU Turn" to the buttons used for turns.
humanMove = new JButton("Human Turn");
computerMove = new JButton("CPU Turn");
// Adds a listener to the buttons to signal the game its time to act.
humanMove.addActionListener(this);
computerMove.addActionListener(this);
// Creates a gridlayout (3,2) with 3 rows and two columns.
JPanel gridpanel = new JPanel(new GridLayout(3,2));
// Labels the rows so the player knows it starts at row Zero - Three.
gridpanel.add(new JLabel("Row Zero", JLabel.LEFT));
gridpanel.add(stickSpace[0]);
gridpanel.add(new JLabel("Row One", JLabel.LEFT));
gridpanel.add(stickSpace[1]);
gridpanel.add(new JLabel("Row Two", JLabel.LEFT));
gridpanel.add(stickSpace[2]);
// Creates another gridlayout this time with 4 rows and 2 columns.
// This sill be used to add the comboboxes, labels, and buttons.
JPanel mainPanel = new JPanel(new GridLayout(4,2));
mainPanel.add(new JLabel("Remove from Row:", JLabel.RIGHT));
mainPanel.add(whatRow);
mainPanel.add(new JLabel("# To Remove:", JLabel.RIGHT));
mainPanel.add(howMany);
mainPanel.add(humanMove);
mainPanel.add(computerMove);
// This adds the gridpanel and the main panel to the visual
// application, but they are still not visiable at this moment.
getContentPane().add(gridpanel, BorderLayout.NORTH);
getContentPane().add(mainPanel, BorderLayout.SOUTH);
// This sections sets the title, size, position on screen, sets it visiable,
// sets the background color, and makes it exit on close of the visual application.
setTitle("The Game of Nim");
setSize(300, 250);
setBackground(Color.yellow);
setVisible(true);
// Creates the actual game to play.
nimgame = new Nimgame();
// Prints out the sticks in each row.
for(int p=0; p<3; p++){
stickSpace[p].setText(nimgame.addSticks(p));
}
}
// Method to handle when an action lister find an action event
public void actionPerformed(ActionEvent e){
// Checks if the humanMove button has been pressed
if(e.getSource() == humanMove){
int foo = whatRow.getSelectedIndex();
int bar = howMany.getSelectedIndex()+1;
nimgame.stickRemove(foo, bar);
for(int p=0; p<3; p++){
stickSpace[p].setText(nimgame.addSticks(p));
}
}
// Checks if the computerMove button has been pressed.
if(e.getSource() == computerMove){
nimgame.computerRandom();
for(int p=0; p<3; p++){
stickSpace[p].setText(nimgame.addSticks(p));
}
}
// Checks to see if the game is over or not.
if(nimgame.isDone()){
JOptionPane.showMessageDialog(null, "Game Over Player Player" + nimgame.whoWon());
}
}
public static void main(String[] args) {
Nim NIM = new Nim();
}
}
Any idea why nothing would be showing up? I figured I forgot to setVisible, but that wasn't the case. Any help would be much appreciated.
public void Nim(){
This isn't a constructor, it's a void method declaration with an awfully confusing name. As you don't declare a constructor at all, you have an implicit default constructor which is called here:
Nim NIM = new Nim();
but the default constructor doesn't do what you'd expect, so you don't see anything. To fix this, change the aforementioned method definition to a constructor definition by removing void:
public Nim() {

Java basic if/else statement state change

please see my attached code below and then my question at the end.
class events extends JFrame{
private JLabel label;
private JButton button;
public events() {
setLayout(new FlowLayout());
button = new JButton("Click for text");
add(button);
label = new JLabel("");
add(label);
event e = new event();
button.addActionListener(e);
}
public class event implements ActionListener {
public void actionPerformed(ActionEvent e) {
int x = 0;
if (x == 0) {
label.setText("the new label");
System.out
.println("setting x to 0 and label to display a label");
x = 1;
System.out.println(x);
} else {
label.setText("newerer label");
System.out.println("i reached the else segment");
x = 0;
System.out.println(x);
}
}
}
public static void main(String args[]) {
events gui = new events();
gui.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
gui.setTitle("Events Test");
gui.setSize(300, 100);
gui.setVisible(true);
}
}
Background: I am learning java and attempting to understand a concept. With this program I was attempting to create a small gui with a button that when clicked would assign a JLabel the String value of "the new label." I wanted to use that same button however to change the label to "newerer label" if clicked a second time and back again if clicked a third. I attempted to do this using an If/ Else statement with a variable x to hold essentially a state of 1 or 0. At the end of each portion of the If/Else i change the state of x to either 1 or 0 appropriately. When attempting to run the program in eclipse however, I have run into some kind of error. I assigned a system.out.println to each portion of the If/Else in an attempt to see how the program switches between the two states but it appears that my else statement is never reached.
Questions:
Is an If/Else statement appropriate to perform such a simple 2 state switch?
Is there a more appropriate way to do this? (i know about switch statements but opted for this as it was only a two state project).
What did I do wrong and why is my Else path never achieved when the state should be 1?
Thank you for your responses,
Pano
Your variable "x" must be declared as a class member.
public class event implements ActionListener{
private int x = 0;
public void actionPerformed(ActionEvent e){
if(x == 0){
label.setText("the new label");
System.out.println("setting x to 0 and label to display a label");
x = 1;
System.out.println(x);
}
else {
label.setText("newerer label");
System.out.println("i reached the else segment");
x = 0;
System.out.println(x);
}
}
}
You are initializing x every time the action listener gets called, so x is always 0. Move x somewhere else, possibly declare it as a class member.
Yes, I personally would use an if/else statement here, although if you are likely to add more states a switch statement may be appropriate, but I think given you have more than 1 line of code in the if/else blocks I would keep it as if/else as it has better readability in my experience.
I guess my answer to 1 covers this!
The reason your else block isn't being reached is that your x variable is only in scope (only exists) inside that method. As soon as you leave the method the value is no longer in scope so as far as your code in concerned it no longer exists. The code P Lalonde posted shows the correct way: having the variable as a member variable (object scope). Read more about member variable scope here: http://docs.oracle.com/javase/tutorial/java/javaOO/variables.html
If you are just looking for a switch of state you could actually do something like:
if( label.getText().equals("the new label") ) {
label.setText("newerer label");
} else {
label.setText("the new label");
}

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