Error: unreported exception java.io.IOException; ??

[jonsamwell]

Hi,

I'm just learning java so bare with me!! i'm just modify some examples i've read through in a book and keep getting the following error at the if statement. could someone tell me what it means and the possible solution??

Error: "unreported exception java.io.IOException; must be caught or declared to be thrown"

Thank you very much

Jon

This is all in public static void main:

       double transaction;
       String line;
       
       java.io.BufferedReader stream_in;
       stream_in = new java.io.BufferedReader(new java.io.InputStreamReader(System.in));
       
       System.out.println("Input the transaction amount.");
       System.out.flush();
       
       if ((line=stream_in.readLine()) !=null) //the error appears here?
           transaction = Double.valueOf(line).doubleValue();   
       else
           transaction = 0;
           
        wallet[0].chargeIt(transaction);
        System.out.println("New Balance: £ " + wallet[0].getBalance());

[Eranga]

Enclose with the try-catch block and see. It'll fix.

        double transaction = 0;
        String line;      
        
        try {
            java.io.BufferedReader stream_in;
            stream_in = new java.io.BufferedReader(new java.io.InputStreamReader(System.in));

            System.out.println("Input the transaction amount.");
            System.out.flush();

            if ((line = stream_in.readLine()) != null) {
                //the error appears here?
                transaction = Double.valueOf(line).doubleValue();
            } else {
                transaction = 0;
            }
        } catch (IOException ex) {
            ex.printStackTrace();
        }
                
        wallet[0].chargeIt(transaction);
        System.out.println("New Balance: £ " + wallet[0].getBalance());

[jonsamwell]

thanks,

but why does it have to be enclosed in a try catch statement in the first place?

[Norm]

unreported exception java.io.IOException; must be caught or declared to be thrown"

Because the compiler says so! Makes for more robust programs if you catch errors and not let them terminate your jvm.

[udayadas]

There are two types of exceptions:

(UE)Unchecked Exceptions (Ex : ArithmaticException)
(CE)Checked Exceptions (Ex : SQLException , IOException etc)

If you using any code that may throw UE then you need not handle them.

On the other hand if such code may throw CE then the compiler will force you to handle them or propagate them.

How to Handle:
============
Put such code in the try/catch block

How to propagate them:
============
Use throws clause in the method declaration

[Eranga]

I think it's better to read some materials related to exception handling in Java, jonsamwell. You get here some well explanations from Norm and udayadas.

Hope you have solve the issue. Any other question?