Having trouble guys this is for my Fahrenheit-Celsius converter class, I can't seem to get my code to recognize the following which makes sure that only numbers are entered into the text field and if not, set as 0:
try {
Double.parseDouble(fahr.getText());
} catch (NumberFormatException e) {
fahr.setText("0");
}
I think it is because of the placement of it within my class. Please check out my full class (I placed it towards the bottom of the code):
public class Temperature implements ActionListener {
private static JTextField fahr;
private static JTextField cels;
private JFrame frame;
private JButton first;
private JButton second;
private double fahrVal;
private Double fahrConv;
private double celsVal;
private double celsConv;
private NumberFormat amountFormat;
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
Temperature window = new Temperature();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
public Temperature() {
initialize();
first.addActionListener((ActionListener) this);
second.addActionListener((ActionListener) this);
}
private void initialize() {
amountFormat = NumberFormat.getNumberInstance();
frame = new JFrame("raB eltiT");
frame.setBounds(100, 50, 350, 350);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().setLayout(null);
first = new JButton("...To Celsius");
first.setBounds(130, 60, 100, 50);
first.setBackground(Color.cyan);
first.setActionCommand("click");
first.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ae) {
JButton src = (JButton) ae.getSource();
//System.out.println("Button labeled " + src.getText() + " was clicked");
}
});
first.addMouseListener(new MouseAdapter() {
public void mouseReleased(MouseEvent me) {
cels.setText(String.valueOf(fahrConv));
}
});
frame.getContentPane().add(first);
second = new JButton("...To Fahrenheit");
second.setBounds(130, 230, 100, 50);
second.setBackground(Color.pink);
second.setActionCommand("instead");
frame.getContentPane().add(second);
second.addMouseListener(new MouseAdapter() {
public void mouseReleased(MouseEvent me) {
fahr.setText(String.valueOf(celsConv));
}
});
// Build the Fahrenheit side
JLabel fLabel = new JLabel("Fahrenheit");
fahr = new JTextField("32");
fahr.setPreferredSize(new Dimension(50,50));
fahr.setHorizontalAlignment(JTextField.CENTER);
JPanel fPanel = new JPanel();
fPanel.setBounds(40, 120,100,100);
fPanel.add(fLabel);
fPanel.add(fahr);
frame.getContentPane().add(fPanel);
JLabel cLabel = new JLabel("Celsius");
cels = new JTextField("0");
cels.setPreferredSize(new Dimension(50,50));
cels.setHorizontalAlignment(JTextField.CENTER);
JPanel cPanel = new JPanel();
cPanel.setBounds(220, 120, 100,100);
cPanel.add(cLabel);
cPanel.add(cels);
frame.getContentPane().add(cPanel);
// Put it all up on the screen
frame.setVisible(true);
try {// if is number
Double.parseDouble(fahr.getText());
} catch (NumberFormatException e) {
fahr.setText("0");
}
}
public void actionPerformed(ActionEvent event) {
String fahrText = fahr.getText();
fahrVal = Double.parseDouble(fahrText);
fahrConv = ((fahrVal - 32)*5)/9;
fahrConv = Double.parseDouble(new DecimalFormat("##.#").format(fahrConv));
String celsText = cels.getText();
celsVal = Double.parseDouble(celsText);
celsConv = 32 + (celsVal * 9 / 5);
celsConv = Double.parseDouble(new DecimalFormat("##.#").format(celsConv));
}
}
The problem is not so much what you're doing but rather where and when you're doing it. You're calling
try {// if is number
Double.parseDouble(fahr.getText());
} catch (NumberFormatException e) {
fahr.setText("0");
}
in the code where you create the GUI, and this then happens before the user has any chance of inputting data into the JTextField, making this code useless. A better solution is to put this code into a listener that responds when the user is ready to submit the data, such as at the start of your ActionListener -- then call return:
Something like:
public void actionPerformed(ActionEvent event) {
try {
Double.parseDouble(fahr.getText());
} catch (NumberFormatException e) {
fahr.setText("0");
// display a JOptionPane error message so the user knows there's been a problem
return; // so the code below isn't called if input in error
}
String fahrText = fahr.getText();
fahrVal = Double.parseDouble(fahrText);
fahrConv = ((fahrVal - 32)*5)/9;
fahrConv = Double.parseDouble(new DecimalFormat("##.#").format(fahrConv));
String celsText = cels.getText();
celsVal = Double.parseDouble(celsText);
celsConv = 32 + (celsVal * 9 / 5);
celsConv = Double.parseDouble(new DecimalFormat("##.#").format(celsConv));
}
Other options:
Other unrelated issues: