Using variable outside of try catch block (Java)

Question

I have a variable that I have delared before a try catch block to make sure I can access it outside of the block

/*
        Try to get a list of all files.
         */

        List<String> result; 
        try( Stream<Path> walk = Files.walk(Paths.get("data"))){
            List<String> result = walk.filter(Files::isRegularFile)
                    .map(x -> x.toString()).collect(Collectors.toList());


        }
        catch(Exception e){
            e.printStackTrace();
            List<String> result = null;
        }


        ListIterator iter = result.listiterator() // cannot resolve symbol

when I take the original declaration out, I get a cannot resolve symbol error. When I keep it in I get a variable already declared error.

What would be the best way to structure this to use the variable outside of the try except clause?

Jist remove the declaration in the try block, only assign it to the already declared variable: `try(...){ result = ...` — NeplatnyUdaj, May 22 '19 at 11:08
See also https://stackoverflow.com/questions/32805813/what-is-the-scope-of-a-variable-defined-inside-java-try-block-why-it-is-not-acc — Raedwald, May 22 '19 at 11:47

Eran · Accepted Answer · 2019-05-22T11:11:03.353

To resolve the compilation error, declare the result variable only before the try-catch block:

List<String> result; 
try( Stream<Path> walk = Files.walk(Paths.get("data"))){
    result = walk.filter(Files::isRegularFile)
            .map(x -> x.toString()).collect(Collectors.toList());
}
catch(Exception e){
    e.printStackTrace();
    result = null;
}

However, note that accessing the result variable after the try-catch block (your result.listiterator() statement) without checking that it's not null may throw a NullPointerException.

You should be asking yourself why you are catching any exception and expecting everything to work fine.

Using variable outside of try catch block (Java)

1 Answers1