Difficulty with string passing...

Hey everyone,

I am having trouble exiting a program normally, rather than it crashing whenever I click the 'cancel' button. :(

This code here is an example of what i want to do/happen...

Code :

---

        double length = 0;  // passing into
        String user_input;  // passing from
        boolean valid = true;  //  to exit the loop (irrelevant) 
 
        do
        {
            user_input = JOptionPane.showInputDialog("Enter the length in metres: ");
 
            try
            { 
                length = Double.parseDouble(user_input); // code to pass string into double.
                valid = true;
            }
 
            catch(NullPointerException error) // catches the error when user clicks the 'cancel' button and exits the program normally.
            {
                System.exit(0);
            }

---

The code above works and doesn't crash or have syntax errors:)

I am trying to implement this with the code below, but to no avail. :(

Code :

---

public static void exampleMethod(String user_input)
    {   
        String choice;
 
     try
       {
        choice = String.parseString(user_input); //<--- No such thing?! WHY!?
       }
 
     catch(NullPointerException error) // catches the error when user clicks the 'cancel' button and exits the program normally.
       {
           System.exit(0);
       }

---

It honestly doesn't bother me what the 'try' function does, it can do anything... or NOTHING i just want the program NOT to crash when i click the 'cancel' button. I even attempted to delete it but the compiler insists ('catch' with no 'try')

I hope this is clear enough... :)

Wow... I have been working on this problem for 36+ hours and I finally figured it out... It was a misunderstanding of the 'try' statement...