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How can I solve a string version of a calculation for a simple calculator? [duplicate]

This question already has answers here:
How to evaluate a math expression given in string form?
(26 answers)
Closed 6 years ago.
This is a simple calculator where the user can type out the calculation and hit enter, and the calculator would determine if it is a valid calculation or not. If it is a valid calculation, the calculation is carried out. If not, an error message is written to the screen.
The calculation is carried out part isn't finished.
Can someone suggest a solutions to the getAnswer() method.
It would be very much appreciated.
import java.awt.ComponentOrientation;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.border.EmptyBorder;
#SuppressWarnings("serial")
public class Calculator extends JFrame{
private interface CalculatorInterface {
public void writeToScreen(String text);
public void clearScreen();
public String getScreenText();
}
private class CalculatorPanel extends JPanel implements CalculatorInterface {
private class NumberPanel extends JPanel implements CalculatorInterface {
private static final int NUMTOTAL = 10;
private CalculatorPanel calcPanel;
private JButton[] numButtons;
public NumberPanel(CalculatorPanel calcPanel) {
this.calcPanel = calcPanel;
buildLayout();
addButtons();
}
private void buildLayout() {
this.setComponentOrientation(ComponentOrientation.RIGHT_TO_LEFT);
GridLayout layout = new GridLayout(4,3);
layout.setHgap(1);
layout.setVgap(1);
this.setLayout(new GridLayout(4,3));
}
private void addButtons() {
numButtons = new JButton[NUMTOTAL];
for(int i = numButtons.length -1; i >= 0 ; i--) {
numButtons[i] = new JButton("" + i);
numButtons[i].setPreferredSize(new Dimension(60,40));
numButtons[i].setFont(new Font("Sans serif", Font.PLAIN, 18));
numButtons[i].addActionListener(
new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
String text = ((JButton)e.getSource()).getText().trim();
if(getScreenText().equals("Invalid Calc")) {
clearScreen();
writeToScreen(text);
}else {
writeToScreen(text);
}
}
});
this.add(numButtons[i]);
}
}
#Override
public void writeToScreen(String text) {
calcPanel.writeToScreen(text);
}
#Override
public void clearScreen() {
calcPanel.clearScreen();
}
#Override
public String getScreenText() {
return calcPanel.getScreenText();
}
}
private class OperPanel extends JPanel implements CalculatorInterface {
private static final int ADD = 0;
private static final int SUB = 1;
private static final int MULT = 2;
private static final int DIV = 3;
private static final int OPENB = 4;
private static final int CLOSEB = 5;
private static final int CLEAR = 6;
private static final int EQL = 7;
private static final int OPERTOTAL = 8;
private CalculatorPanel calcPanel;
private JButton[] operButtons;
public OperPanel(CalculatorPanel calcPanel) {
this.calcPanel = calcPanel;
buildLayout();
addButtons();
}
private void buildLayout() {
GridLayout layout = new GridLayout(4,1);
layout.setHgap(1);
layout.setVgap(1);
this.setLayout(new GridLayout(4,1));
}
private void addButtons() {
operButtons = new JButton[OPERTOTAL];
operButtons[ADD] = makeButton(ADD, "+");
operButtons[SUB] = makeButton(SUB, "-");
operButtons[MULT] = makeButton(MULT, "*");
operButtons[DIV] = makeButton(DIV, "/");
operButtons[CLEAR] = makeButton(CLEAR, "CL");
operButtons[EQL] = makeButton(EQL, "=");
operButtons[OPENB] = makeButton(OPENB, "(");
operButtons[CLOSEB] = makeButton(CLOSEB, ")");
for(JButton button: operButtons) {
this.add(button);
}
}
private JButton makeButton(int index, String label) {
operButtons[index] = new JButton(label);
operButtons[index].addActionListener(
new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
String text = ((JButton)e.getSource()).getText();
if(text.equals("=")) {
String screenText = getScreenText();
clearScreen();
try {
writeToScreen(getAnswer(screenText));
}catch(Exception excep) {
writeToScreen("Invalid Calc");
}
}else if(text.equals("CL")) {
clearScreen();
}else {
writeToScreen(text);
}
}
});
return operButtons[index];
}
private String getAnswer(String text) throws Exception {
/*I'm trying to solve for any input by the user e.g
*(the stuff in square brackets represents what is displayed
* on the screen:.
*[1+1] (hits equals) [2]
*[1+2-3] (hits equals) [0]
*[1+2*3] (hits equals) [7]
*[10*(14+1/2)] (hits equals) [145]
*/
throw new Exception();
}
#Override
public String getScreenText() {
return calcPanel.getScreenText();
}
#Override
public void clearScreen() {
calcPanel.clearScreen();
}
#Override
public void writeToScreen(String text) {
calcPanel.writeToScreen(text);
}
}
private NumberPanel numPanel;
private OperPanel operPanel;
private JTextField calcScreen;
public CalculatorPanel(JTextField calcScreen) {
this.calcScreen = calcScreen;
buildNumPanel();
buildOperPanel();
buildCalcPanel();
}
private void buildNumPanel() {
this.numPanel = new NumberPanel(this);
}
private void buildOperPanel() {
this.operPanel = new OperPanel(this);
}
private void buildCalcPanel() {
this.setLayout(new BoxLayout(this, BoxLayout.X_AXIS));
this.add(numPanel);
this.add(operPanel);
}
#Override
public void writeToScreen(String text) {
calcScreen.setText(getScreenText() + text);
}
#Override
public String getScreenText() {
return calcScreen.getText();
}
#Override
public void clearScreen() {
calcScreen.setText("");
}
}
private JPanel mainPanel;
private JTextField calcScreen;
private CalculatorPanel calcPanel;
public Calculator() {
buildScreen();
buildCalcPanel();
buildMainPanel();
buildCalculator();
}
private void buildScreen() {
this.calcScreen = new JTextField();
this.calcScreen.setPreferredSize(new Dimension(150,50));
this.calcScreen.setHorizontalAlignment(JTextField.CENTER);
this.calcScreen.setFont(new Font("Sans serif", Font.PLAIN, 30));
}
private void buildCalcPanel() {
this.calcPanel = new CalculatorPanel(this.calcScreen);
}
private void buildMainPanel() {
this.mainPanel = new JPanel();
this.mainPanel.setBorder(new EmptyBorder(10,10,10,10));
this.mainPanel.setLayout(new BoxLayout(this.mainPanel, BoxLayout.Y_AXIS));
this.mainPanel.add(calcScreen);
this.mainPanel.add(calcPanel);
}
private void buildCalculator() {
this.add(mainPanel);
this.setTitle("Calculator");
this.pack();
this.setLocationRelativeTo(null);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setVisible(true);
}
public static void main(String[] args) {
#SuppressWarnings("unused")
Calculator calc = new Calculator();
}
}
How can I check to see if a string is a valid calculation for a simple calculator?
Edit 1: Fixed a silly bug in the makeButton() method were I passed in the text of the button to be verified instead of the text on screen. (I'm an idiot.)
Edit 2: Removed the isValid(String text) from the code and make it so the getAnswer() method just threw an exception if input is not a valid calculation.

As well mentioned in a previous StackOverflow answer (Evaluating a math expression given in string form), you could use Javascript's ScriptEngine to calculate expressions based on strings that you would retrieve from the Text Field. Place it in a try-catch block first to see if there's an error in the expression. In the catch block, set the variable storing whether its a valid expression or not to false.
boolean validExpression = true;
ScriptEngineManager mgr = new ScriptEngineManager();
ScriptEngine engine = mgr.getEngineByName("JavaScript");
String input = textField.getText() // Modify this to whatever variable you have assigned to your text field
try {
System.out.println(engine.eval(foo));
}
catch (ScriptException e) {
validExpression = false;
System.out.println("Invalid Expression");
}
Make sure you include the following imports:
import javax.script.ScriptEngineManager;
import javax.script.ScriptEngine;
import javax.script.ScriptException;
Although you could try to implement Shunting-Yard Algorithm or another arithmetic parser, this is simply a way more pragmatic solution.

MVC Pattern JButton ActionListener not Responding

So I'm trying to create a simple test program where the user can enter something into a JTextField, click the "add" JButton, and a JTextArea will add the users string to the the JTextArea (continuously appending with new line).
I added the actionListener for the button and have a stateChanged and an update method, but nothing happens when I click the add button. No errors either. Could someone please point me in the right direction?
Here's my code:
MVCTester (main)
public class MVCTester {
public static void main(String[] args) {
// TODO Auto-generated method stub
MVCController myMVC = new MVCController();
MVCViews myViews = new MVCViews();
myMVC.attach(myViews);
}
}
MVCController
import java.util.ArrayList;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
public class MVCController {
MVCModel model;
ArrayList<ChangeListener> listeners;
public MVCController(){
model = new MVCModel();
listeners = new ArrayList<ChangeListener>();
}
public void update(String input){
model.setInputs(input);
for (ChangeListener l : listeners)
{
l.stateChanged(new ChangeEvent(this));
}
}
public void attach(ChangeListener c)
{
listeners.add(c);
}
}
MVCModel
import java.util.ArrayList;
public class MVCModel {
private ArrayList<String> inputs;
MVCModel(){
inputs = new ArrayList<String>();
}
public ArrayList<String> getInputs(){
return inputs;
}
public void setInputs(String input){
inputs.add(input);
}
}
MVCViews
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
public class MVCViews implements ChangeListener {
private JTextField input;
private JTextArea echo;
private ArrayList<String> toPrint = new ArrayList<String>();
MVCController controller;
MVCViews(){
controller = new MVCController();
JPanel myPanel = new JPanel();
JButton addButton = new JButton("add");
echo = new JTextArea(10,20);
echo.append("Hello there! \n");
echo.append("Type something below!\n");
myPanel.setLayout(new BorderLayout());
myPanel.add(addButton, BorderLayout.NORTH);
input = new JTextField();
final JFrame frame = new JFrame();
frame.add(myPanel, BorderLayout.NORTH);
frame.add(echo, BorderLayout.CENTER);
frame.add(input, BorderLayout.SOUTH);
addButton.addActionListener(new ActionListener(){
#Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
controller.update(input.getText());
}
});
frame.pack();
frame.setVisible(true);
}
#Override
public void stateChanged(ChangeEvent e) {
// TODO Auto-generated method stub
toPrint = controller.model.getInputs();
for(String s: toPrint){
echo.append(s + "\n");
}
}
}
This is my first time trying to follow MVC format, so there might be issues with the model itself as well. Feel free to point them out. Thank you for your help!

The controller within the GUI is not the same controller that is created in main. Note how many times you call new MVCController() in your code above -- it's twice. Each time you do this, you're creating a new and distinct controller -- not good. Use only one. You've got to pass the one controller into the view. You can figure out how to do this. (hint, a setter or constructor parameter would work).
hint 2: this could work: MVCViews myViews = new MVCViews(myMVC);
one solution:
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import javax.swing.*;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
public class MVCTester {
public static void main(String[] args) {
MVCController myMVC = new MVCController();
MVCViews myViews = new MVCViews(myMVC);
myMVC.attach(myViews);
// myViews.setController(myMVC); // or this could do it
}
}
class MVCController {
MVCModel model;
ArrayList<ChangeListener> listeners;
public MVCController() {
model = new MVCModel();
listeners = new ArrayList<ChangeListener>();
}
public void update(String input) {
model.setInputs(input);
for (ChangeListener l : listeners) {
l.stateChanged(new ChangeEvent(this));
}
}
public void attach(ChangeListener c) {
listeners.add(c);
}
}
class MVCModel {
private ArrayList<String> inputs;
MVCModel() {
inputs = new ArrayList<String>();
}
public ArrayList<String> getInputs() {
return inputs;
}
public void setInputs(String input) {
inputs.add(input);
}
}
class MVCViews implements ChangeListener {
private JTextField input;
private JTextArea echo;
private ArrayList<String> toPrint = new ArrayList<String>();
MVCController controller;
MVCViews(final MVCController controller) {
// !! controller = new MVCController();
this.controller = controller;
JPanel myPanel = new JPanel();
JButton addButton = new JButton("add");
echo = new JTextArea(10, 20);
echo.append("Hello there! \n");
echo.append("Type something below!\n");
myPanel.setLayout(new BorderLayout());
myPanel.add(addButton, BorderLayout.NORTH);
input = new JTextField();
final JFrame frame = new JFrame();
frame.add(myPanel, BorderLayout.NORTH);
frame.add(echo, BorderLayout.CENTER);
frame.add(input, BorderLayout.SOUTH);
addButton.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
if (controller != null) {
controller.update(input.getText());
}
}
});
frame.pack();
frame.setVisible(true);
}
public void setController(MVCController controller) {
this.controller = controller;
}
#Override
public void stateChanged(ChangeEvent e) {
if (controller != null) {
toPrint = controller.model.getInputs();
for (String s : toPrint) {
echo.append(s + "\n");
}
}
}
}

Java keeps adding buttons! - JFrames - [closed]

Closed. This question needs details or clarity. It is not currently accepting answers.
Want to improve this question? Add details and clarify the problem by editing this post.
Closed 8 years ago.
Improve this question
Alright, so, I am trying to make a game using a JFrame that, when you click a button, adds money, and show update some text(a JLabel).
You see, it should just update the Windows.Money variable and display ONLY the new variable on the screen, but, it adds more buttons. Please note: The money part works fine.
It's just that Java doesn't want to replace, only add.
Code:
package dev.bobdabiulder.classic.main;
import javax.swing.JLabel;
public class Bucket extends Window{
private static final long serialVersionUID = 1L;
public Bucket() throws InterruptedException {
for(int i = 0; !Window.Paused; ) {
Window.Money += 2;
this.wait(1000);
}
Window.Buckets++;
Window.BucketCounter = new JLabel("You have: " + Window.Buckets + " buckets!");
}
}
In the Windows class...
package dev.bobdabiulder.classic.main;
import java.awt.Button;
import java.awt.Component;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
public class Window extends JFrame{
public static long Money = 0;
private static final long serialVersionUID = 1L;
private static Thread t1 = new Thread();
private static Thread t2 = new Thread();
private static Thread t3 = new Thread();
private static Thread t4 = new Thread();
private static Thread t5 = new Thread();
public JButton bucket = new JButton("Buy a Bucket!");
public JButton add$ = new JButton("Add Money!");
public JLabel money = new JLabel(Money + "");
public static long Buckets = 0;
public static JLabel BucketCounter = new JLabel("You have: " + Buckets + " buckets!");
public static JPanel buck = new JPanel();
public static boolean Paused = false;
static JFrame jf = new JFrame("Lol!");
//Window Method
public Window() {
jf.setVisible(true);
jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
buck.add(bucket);
buck.add(money);
buck.add(add$);
buck.add(BucketCounter);
jf.setSize(500, 500);
jf.add(buck);
bucket.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
if(e.getSource().equals(bucket)) {
try {
new Bucket();
} catch (Exception e1) {
e1.printStackTrace();
}
}
System.out.println("Action Performed!");
}
});
pack();
}
//End of ActionPerformed
//Start of start()
public static void start() {
t1.start();
t2.start();
t3.start();
t4.start();
t5.start();
}
//
//
//
#SuppressWarnings("deprecation")
public static void stop() {
t1.stop();
t2.stop();
t3.stop();
t4.stop();
t5.stop();
}
}
I made some requested edits, and I get errors where I put *, the errors all read:
Cannot make a static reference to the non-static field Window.(anything),
Error Spots:
for(int i = 0; !*Window.Paused; ) {
*Window.Money += 2;
this.wait(1000);
}
*Window.Buckets++;
*Window.BucketCounter = new JLabel("You have: " + *Window.Buckets + " buckets!");

Brief example of MVC, well really Model-View. What this does is uses a Swing Timer and not Threads (not directly that is) to increment a JLabel held in a different class. It also uses PropertyChangeListener and support to notify the view (the GUI) of changes in the state of the model.
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.text.NumberFormat;
import javax.swing.*;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import javax.swing.event.SwingPropertyChangeSupport;
/**
* http://stackoverflow.com/q/22620807/522444
* http://stackoverflow.com/a/22621767/522444
* #author Pete
*
*/
#SuppressWarnings("serial")
public class ShortMvc extends JPanel {
private JTextField moneyField = new JTextField(10);
private JTextField bucketField = new JTextField(10);
private MoneyModel model = new MoneyModel();
private Timer timer = new Timer(model.getTimerDelay(), new TimerListener());
private JButton moneyButton = new JButton("Add Money");
private JButton bucketButton = new JButton("Add Bucket");
public ShortMvc() {
moneyField.setEditable(false);
moneyField.setFocusable(false);
bucketField.setEditable(false);
bucketField.setFocusable(false);
bucketField.setText(String.valueOf(model.getBuckets()));
add(new JLabel("Money:"));
add(moneyField);
add(moneyButton);
add(new JLabel("Buckets:"));
add(bucketField);
add(bucketButton);
moneyButton.getModel().addChangeListener(new MoneyBtnModelListener());
moneyButton.setMnemonic(KeyEvent.VK_M);
bucketButton.addActionListener(new BucketButtonListener());
bucketButton.setMnemonic(KeyEvent.VK_B);
model.addPropertyChangeListener(new ModelListener());
timer.setInitialDelay(0);
}
private class BucketButtonListener implements ActionListener {
#Override
public void actionPerformed(ActionEvent e) {
model.incrementBuckets();
}
}
private class MoneyBtnModelListener implements ChangeListener {
private boolean pressed = false;
#Override
public void stateChanged(ChangeEvent e) {
ButtonModel model = (ButtonModel) e.getSource();
if (pressed == model.isPressed()) {
return;
}
pressed = model.isPressed();
if (pressed) {
timer.start();
} else {
timer.stop();
}
}
}
private class TimerListener implements ActionListener {
#Override
public void actionPerformed(ActionEvent e) {
model.incrementMoney(model.getMoneyIncrementAmount());
}
}
private class ModelListener implements PropertyChangeListener {
private NumberFormat moneyFormat = NumberFormat.getCurrencyInstance();
public ModelListener() {
moneyField.setText(moneyFormat.format(model.getMoney()));
}
#Override
public void propertyChange(PropertyChangeEvent pcEvt) {
if (MoneyModel.MONEY.equals(pcEvt.getPropertyName())) {
moneyField.setText(moneyFormat.format(model.getMoney()));
}
else if (MoneyModel.BUCKETS.equals(pcEvt.getPropertyName())) {
int buckets = model.getBuckets();
bucketField.setText(String.valueOf(buckets));
timer.setDelay(model.getTimerDelay());
}
}
}
private static void createAndShowGui() {
JFrame frame = new JFrame("Short Mvc");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(new ShortMvc());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
class MoneyModel {
public static final String MONEY = "money";
public static final String BUCKETS = "buckets";
private static final int INIT_TIMER_DELAY = 500;
public static final long MONEY_INCREMENT_AMOUNT = 2L;
private long money = 0L;
private int buckets = 1;
private int timerDelay = INIT_TIMER_DELAY;
private SwingPropertyChangeSupport pcSupport = new SwingPropertyChangeSupport(
this);
public void setMoney(long money) {
long oldValue = this.money;
long newValue = money;
this.money = money;
pcSupport.firePropertyChange(MONEY, oldValue, newValue);
}
public long getMoneyIncrementAmount() {
return MONEY_INCREMENT_AMOUNT;
}
public void incrementMoney(long addToMoney) {
long oldValue = this.money;
long newValue = money + addToMoney;
this.money = newValue;
pcSupport.firePropertyChange(MONEY, oldValue, newValue);
}
public long getMoney() {
return money;
}
public void setBuckets(int buckets) {
int oldValue = this.buckets;
int newValue = buckets;
this.buckets = newValue;
timerDelay = INIT_TIMER_DELAY / buckets;
pcSupport.firePropertyChange(BUCKETS, oldValue, newValue);
}
public void incrementBuckets(int incrementAmount) {
int newValue = this.buckets + incrementAmount;
setBuckets(newValue);
}
// increment by one
public void incrementBuckets() {
incrementBuckets(1);
}
public int getBuckets() {
return buckets;
}
public int getTimerDelay() {
return timerDelay;
}
public void addPropertyChangeListener(PropertyChangeListener listener) {
pcSupport.addPropertyChangeListener(listener);
}
public void removePropertyChangeListener(PropertyChangeListener listener) {
pcSupport.removePropertyChangeListener(listener);
}
}
Note that I can't use an ActionListener for this to work since an ActionListener only gets activated when the button is released. I'm assuming that you want to accumulate money when the button is pressed, and then stop accumulating when it is released. To do this, you must extract the JButton's model, add a ChangeListener to it, and then react to changes to the model's isPressed() method. I use it to start and stop the Swing Timer that increments the model.
Edit
Next iteration with better MVC (model-view-control) separation:
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.text.NumberFormat;
import javax.swing.*;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import javax.swing.event.SwingPropertyChangeSupport;
import javax.swing.text.JTextComponent;
/**
* http://stackoverflow.com/q/22620807/522444
* http://stackoverflow.com/a/22621767/522444
* #author Pete
*
*/
public class ShortMvc {
private static void createAndShowGui() {
ShortView view = new ShortView();
MoneyModel model = new MoneyModel();
ShortControl control = new ShortControl(model, view);
control.init();
JFrame frame = new JFrame("Short MVC");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(view.getMainPanel());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
class ShortView {
private JTextField moneyField = new JTextField(10);
private JTextField bucketField = new JTextField(10);
private JButton moneyButton = new JButton();
private JButton bucketButton = new JButton();
private JPanel mainPanel = new JPanel();
public ShortView() {
moneyField.setEditable(false);
moneyField.setFocusable(false);
bucketField.setEditable(false);
bucketField.setFocusable(false);
mainPanel.add(new JLabel("Money:"));
mainPanel.add(moneyField);
mainPanel.add(moneyButton);
mainPanel.add(new JLabel("Buckets:"));
mainPanel.add(bucketField);
mainPanel.add(bucketButton);
}
public JComponent getMainPanel() {
return mainPanel;
}
public JTextComponent getMoneyField() {
return moneyField;
}
public JTextComponent getBucketField() {
return bucketField;
}
public AbstractButton getMoneyButton() {
return moneyButton;
}
public AbstractButton getBucketButton() {
return bucketButton;
}
}
#SuppressWarnings("serial")
class ShortControl {
private MoneyModel model;
private ShortView view;
private Timer timer;
private MoneyBtnAction moneyBtnAction = new MoneyBtnAction("Add Money", KeyEvent.VK_M);
private BucketButtonAction bucketAction = new BucketButtonAction("Add Buckets", KeyEvent.VK_B);
public ShortControl(MoneyModel model, ShortView view) {
this.model = model;
this.view = view;
timer = new Timer(model.getTimerDelay(), new TimerListener());
}
public void init() {
timer.setInitialDelay(0);
view.getBucketField().setText(String.valueOf(model.getBuckets()));
view.getMoneyButton().setAction(moneyBtnAction);
view.getMoneyButton().getModel().addChangeListener(moneyBtnAction);
view.getBucketButton().setAction(bucketAction);
model.addPropertyChangeListener(new ModelListener());
}
private class BucketButtonAction extends AbstractAction {
public BucketButtonAction(String name, int mnemonic) {
super(name);
putValue(MNEMONIC_KEY, mnemonic);
}
#Override
public void actionPerformed(ActionEvent e) {
model.incrementBuckets();
}
}
private class MoneyBtnAction extends AbstractAction implements ChangeListener {
private boolean pressed = false;
public MoneyBtnAction(String name, int mnemonic) {
super(name);
putValue(MNEMONIC_KEY, mnemonic);
}
#Override
public void actionPerformed(ActionEvent e) {
// empty
}
#Override
public void stateChanged(ChangeEvent e) {
ButtonModel model = (ButtonModel) e.getSource();
if (pressed == model.isPressed()) {
return;
}
pressed = model.isPressed();
if (pressed) {
timer.start();
} else {
timer.stop();
}
}
}
private class ModelListener implements PropertyChangeListener {
private NumberFormat moneyFormat = NumberFormat.getCurrencyInstance();
public ModelListener() {
view.getMoneyField().setText(moneyFormat.format(model.getMoney()));
}
#Override
public void propertyChange(PropertyChangeEvent pcEvt) {
if (MoneyModel.MONEY.equals(pcEvt.getPropertyName())) {
view.getMoneyField().setText(moneyFormat.format(model.getMoney()));
}
else if (MoneyModel.BUCKETS.equals(pcEvt.getPropertyName())) {
int buckets = model.getBuckets();
view.getBucketField().setText(String.valueOf(buckets));
timer.setDelay(model.getTimerDelay());
}
}
}
private class TimerListener implements ActionListener {
#Override
public void actionPerformed(ActionEvent e) {
model.incrementMoney(model.getMoneyIncrementAmount());
}
}
}
class MoneyModel {
public static final String MONEY = "money";
public static final String BUCKETS = "buckets";
private static final int INIT_TIMER_DELAY = 500;
public static final long MONEY_INCREMENT_AMOUNT = 2L;
private long money = 0L;
private int buckets = 1;
private int timerDelay = INIT_TIMER_DELAY;
private SwingPropertyChangeSupport pcSupport = new SwingPropertyChangeSupport(
this);
public void setMoney(long money) {
long oldValue = this.money;
long newValue = money;
this.money = money;
pcSupport.firePropertyChange(MONEY, oldValue, newValue);
}
public long getMoneyIncrementAmount() {
return MONEY_INCREMENT_AMOUNT;
}
public void incrementMoney(long addToMoney) {
long oldValue = this.money;
long newValue = money + addToMoney;
this.money = newValue;
pcSupport.firePropertyChange(MONEY, oldValue, newValue);
}
public long getMoney() {
return money;
}
public void setBuckets(int buckets) {
int oldValue = this.buckets;
int newValue = buckets;
this.buckets = newValue;
timerDelay = INIT_TIMER_DELAY / buckets;
pcSupport.firePropertyChange(BUCKETS, oldValue, newValue);
}
public void incrementBuckets(int incrementAmount) {
int newValue = this.buckets + incrementAmount;
setBuckets(newValue);
}
// increment by one
public void incrementBuckets() {
incrementBuckets(1);
}
public int getBuckets() {
return buckets;
}
public int getTimerDelay() {
return timerDelay;
}
public void addPropertyChangeListener(PropertyChangeListener listener) {
pcSupport.addPropertyChangeListener(listener);
}
public void removePropertyChangeListener(PropertyChangeListener listener) {
pcSupport.removePropertyChangeListener(listener);
}
}

Ok, this should help a bit... missing Timer but you can get an idea of how to manage ActionListeners:
Main class
public class WindowInit{
public static void main(String args[]){
WindowHelp wh = new WindowHelp();
}
}
WindowHelp (This one does the magic)
import java.awt.*;
import javax.swing.*;
import javax.swing.event.*;
import java.awt.event.*;
import javax.swing.event.*;
public class WindowHelp{
JButton b1;
JButton b2;
JLabel label;
long money;
long buckets;
JFrame jf;
Timer timer;
public WindowHelp(){
money = 0;
buckets = 0;
b1 = new JButton("Add buckets");
b2 = new JButton("Add money");
label = new JLabel("");
jf = new JFrame("My Game");
b1.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
buckets += 2;
label.setText("Buckets: " + buckets);
}
});
b1.setBounds(50,50,100,30);
b2.setBounds(200,50,100,30);
label.setBounds(300,50,200,30);
jf.add(b1);
jf.add(b2);
jf.add(label);
jf.setSize(500,600);
jf.setVisible(true);
jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}
Yes, one is the main class you compile "WindowInit" and run that one.
For timers, gimme some time while I implement it.

How to invoke a static method(reflection) with arguments given by a user

I have created an app which displays: methods, fields, constructors of a class(typed in by user a JTextField). It adds those methods, fields, constructors to three separate JLists.
I want to give user possibility to choose one metod from the list and then invoke it(only those methods which parameters are type of String or int).
I do not know how to get information how many arguments the method needs and then what type is every parameter(String or int) and how to pass them to method.invoke(ARGUMENTS).
The working code:
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import javax.swing.DefaultListModel;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
import javax.swing.border.LineBorder;
public class Zadanie extends JFrame {
JList<Method> mList;
JList<Field> fList;
JList<Constructor> cList;
DefaultListModel<Method> modelM;
DefaultListModel<Field> modelF;
DefaultListModel<Constructor> modelC;
JTextField txt;
JButton buttonOK, buttonReset;
JPanel centerPanel, topPanel, buttonPanel;
boolean reseted;
public Zadanie() {
reseted = true;
}
public void createGUI() {
setSize(800, 600);
add(topPanel = new JPanel(new BorderLayout()), BorderLayout.NORTH);
topPanel.add(txt = new JTextField("Person"), BorderLayout.CENTER);
topPanel.add(buttonPanel = new JPanel(new GridLayout(1, 2)), BorderLayout.EAST);
buttonPanel.add(buttonOK = new JButton("OK"));
buttonPanel.add(buttonReset = new JButton("RESET"));
topPanel.setBorder(new LineBorder(Color.red, 1));
add(centerPanel = new JPanel(new GridLayout(3, 1)), BorderLayout.CENTER);
centerPanel.setBorder(new LineBorder(Color.green, 1));
modelM = new DefaultListModel<Method>();
modelF = new DefaultListModel<Field>();
modelC = new DefaultListModel<Constructor>();
centerPanel.add(new JScrollPane(mList = new JList<Method>(modelM), JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS));
centerPanel.add(new JScrollPane(fList = new JList<Field>(modelF), JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS));
centerPanel.add(new JScrollPane(cList = new JList<Constructor>(modelC), JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS));
setDefaultCloseOperation(EXIT_ON_CLOSE);
createListeners();
setVisible(true);
}
private void createListeners() {
txt.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent arg0) {
buttonOK.doClick();
}
});
buttonOK.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
try {
if (reseted) {//szukanie klasy
reseted = false;
Class<?> fetchedClass = Class.forName(txt.getText());
Method[] methods = fetchedClass.getDeclaredMethods();
System.out.println(methods.length);
for (Method method : methods) {
modelM.addElement(method);
}
Field[] fields = fetchedClass.getFields();
for (Field field : fields) {
modelF.addElement(field);
}
Constructor[] constructors = fetchedClass.getConstructors();
for (Constructor constructor : constructors) {
modelC.addElement(constructor);
}
} else {//odpalanie metod
}
} catch (ClassNotFoundException e1) {
reseted = true;
e1.printStackTrace();
}
}
});
buttonReset.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent arg0) {
reseted = true;
modelM.clear();
modelF.clear();
modelC.clear();
}
});
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new Zadanie().createGUI();
}
});
}
}
class Person {
int age;
String name;
public Person(int age, String name) {
super();
this.age = age;
this.name = name;
}
public void doSth(){
System.out.println("Do sth 1");
}
public void doSth(int a){
System.out.println("Do sth 2");
}
public void doSth(String s){
System.out.println("Do sth 3");
}
public static void doSthStatic(){
System.out.println("Do sth static");
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
#Override
public String toString() {
return "Osoba [age=" + age + ", name=" + name + "]";
}
public static void main(String[] args) {
Person o = new Person(42, "fas");
System.out.println(o.getClass().getCanonicalName());
}
}

This may help you
public class Sample {
public String appendStrings(String a,String b) {
return a.concat(b);
}
}
Now I am going to invoke appendStrings using Java reflection.
public class Test {
public static void main(String[] args) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException {
Sample sample=new Sample();
Method method=Sample.class.getDeclaredMethod("appendStrings", String.class, String.class);
System.out.println(method.invoke(sample, "Hello", "World"));
}
}
Out put
HelloWorld

there is apache commons lib which does it with 1 line of code.
org.apache.commons.lang.reflect.MethodUtils.invokeExactStaticMethod(Class class, String methodName, Object[] arguments)
Invokes a static method whose parameter types match exactly the object types.

Have I got the right idea with SwingWorker

I just wanted to double check my implementation for using a SwingWorker thread is done the correct and clean way. Also, just need verification my implementation of the model-view-controller pattern is correct and clean as well. Everything seems to be working as it should and it seems a nice simple implementation to me.
The Model class.
package Model;
public class Model
{
private int counter;
private boolean go = true;
public Void go()
{
counter = 0;
while(go)
{
counter++;
System.out.println(counter);
}
return null;
}
public int getCounter()
{
return counter;
}
public String getCounterToString()
{
return Integer.toString(counter);
}
public void setGo(boolean value)
{
this.go = value;
}
}
The View class.
package View;
import java.awt.*;
import javax.swing.*;
public class View extends JFrame
{
private JPanel topPanel, bottomPanel;
private JTextArea messageArea;
private JButton startButton, cancelButton;
private JLabel messageLabel;
private JScrollPane scrollPane;
public View()
{
setSize(250, 220);
setTitle("View");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
topPanel = new JPanel();
bottomPanel = new JPanel();
messageArea = new JTextArea(8, 20);
messageArea.setEditable(true);
scrollPane = new JScrollPane(messageArea);
messageLabel = new JLabel("Message Area");
topPanel.setLayout(new BorderLayout());
topPanel.add(messageLabel, "North");
topPanel.add(scrollPane, "South");
startButton = new JButton("START");
cancelButton = new JButton("CANCEL");
bottomPanel.setLayout(new GridLayout(1, 2));
bottomPanel.add(startButton);
bottomPanel.add(cancelButton);
Container cp = getContentPane();
cp.add(topPanel, BorderLayout.NORTH);
cp.add(bottomPanel, BorderLayout.SOUTH);
}
public JButton getStartButton()
{
return startButton;
}
public JButton getCancelButton()
{
return cancelButton;
}
public void setMessageArea(String message)
{
messageArea.append(message + "\n");
}
}
The Controller class.
package Controller;
import java.awt.event.*;
import javax.swing.SwingWorker;
import Model.*;
import View.*;
public class Controller implements ActionListener
{
private Model theModel;
private View theView;
private SwingWorker<Void, Void> worker;
public Controller(Model model, View view)
{
this.theModel = model;
this.theView = view;
view.getStartButton().addActionListener(this);
view.getCancelButton().addActionListener(this);
}
public void actionPerformed(ActionEvent ae)
{
Object buttonClicked = ae.getSource();
if(buttonClicked.equals(theView.getStartButton()))
{
theModel.setGo(true);
worker = new SwingWorker<Void, Void>()
{
#Override
protected Void doInBackground()
{
//theView.setMessageArea(theModel.getCounterToString());
return theModel.go();
}
#Override
protected void done()
{
//theView.setMessageArea(theModel.getCounterToString());
}
};
worker.execute();
}
else if(buttonClicked.equals(theView.getCancelButton()))
{
theModel.setGo(false);
}
}
}
The Main class.
package swinginfiniteloop;
import Model.*;
import View.*;
import Controller.*;
public class Main
{
public static void main(String[] args)
{
Model model = new Model();
View view = new View();
Controller controller = new Controller(model, view);
view.setVisible(true);
}
}