Handling exceptions problem

for my class we have to throw an exception if the user inputs any characters into a text field (its for converting fahrenheit to celsius). anyway, here is the part of my code that does this:
String input = "";
double temp;
boolean test = true;
//try statement
try
     input = fahr.getText();
//catch statement
catch (NumberFormatException f)
     JOptionPane.showMessageDialog(null, "Invalid data was entered, try again.");
     test = false;
if (test)
     //convert to celsius
     temp = (Double.parseDouble(input) - 32) / 1.8;
     //display result
     JOptionPane.showMessageDialog(null, input + " degrees Fahrenheit is "
                         + temp + " degrees Celsius.");
}i thought it would catch the exception, but this is what i get when i input a letter into the text field (it comes up in the dos prompt):
java.lang.NumberFormatException: For input string: "y"
        at java.lang.NumberFormatException.forInputString(NumberFormatException.
java:48)
        at java.lang.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1
207)
        at java.lang.Double.parseDouble(Double.java:220)
        at TemperatureWindowR$CalcButtonListener.actionPerformed(TemperatureWind
owR.java:96)
        at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:17
86)
        at javax.swing.AbstractButton$ForwardActionEvents.actionPerformed(Abstra
ctButton.java:1839)
        at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel
.java:420)
        at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:258
        at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonL
istener.java:245)
        at java.awt.Component.processMouseEvent(Component.java:5100)
        at java.awt.Component.processEvent(Component.java:4897)
        at java.awt.Container.processEvent(Container.java:1569)
        at java.awt.Component.dispatchEventImpl(Component.java:3615)
        at java.awt.Container.dispatchEventImpl(Container.java:1627)
        at java.awt.Component.dispatchEvent(Component.java:3477)
        at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:3483
        at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3198)
        at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3128)
        at java.awt.Container.dispatchEventImpl(Container.java:1613)
        at java.awt.Window.dispatchEventImpl(Window.java:1606)
        at java.awt.Component.dispatchEvent(Component.java:3477)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:456)
        at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchTh
read.java:201)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThre
ad.java:151)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:145)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:137)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:100)

I only glanced at your code, but it looks like you have most of the right pieces, just in the wrong places a little bit. Roughly like this: boolean accepted = false;
while (!accepted) { // need to keep looping until they get it right.
    try {
        read user input
        // This needs to be inside the try, since it throws the exception we want to catch
        temp = Double.parseDouble(...) etc.
        // If we got this far, then the above didn't throw, so it's a number
        accepted = true;
    catch (NumberFormatException exc) {
        // since we didn't get far enought to set accepted to true, we'll go through the loop again
        "Try again" message
process temp

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