Missing return statement error even with return statement at the end of method

Question

I have this method to search for files and store them into a list and return it. The problem is that I get an "This method must return a result of type List" even I have a return statement of type List at the end of it.

public List<String> cautaFisiere(String root) {
    List<String> list = new ArrayList<String>();
    File[] file = new File(root).listFiles();
    if (file == null) {
        return ;
    }
    for (File x : file) {
        if (x.getName().toLowerCase().contains(fileName.toLowerCase())) {
            System.out.println(x.getName() + " " + x.getPath());
        }
        String path = x.getPath();
        if (x.isDirectory()) {
            cautaFisiere(path);

        }

    }
    return list;
}

the error is on the 5th line in my code

Have a look at `return ;` - you're probably told that this is the line the error is related to by your IDE or the compiler. — Thomas, Jan 17 '17 at 14:24
You have to return some value, you probably want either `return null;` or `return Collections.emptyList();`. — Quota, Jan 17 '17 at 14:24

Rauno · Answer 1 · 2017-01-17T14:27:39.353

2

You can fix that by returning null.

 if (file == null) {
    return null;
 }

Edit: I suppose you're right.

if (file == null) {
   return list;
}

edited Jan 17 '17 at 14:27

answered Jan 17 '17 at 14:24

Rauno

616
8
22

Bad idea. He should return the (empty) list – Stephen C Jan 17 '17 at 14:25
1

@StephenC - Or perhaps throw an exception. – Ted Hopp Jan 17 '17 at 14:28

davidxxx · Accepted Answer · 2017-01-17T14:26:47.440

2

public List<String> cautaFisiere(String root) {
  ...
  List<String> list = new ArrayList<String>();
  ...

    if (file == null) {
        return ;
    }
  ...
}

is not legal as the method should return a List of String.

So you could write :

if (file == null) {
    return null ;
}

or

if (file == null) {
    return list;
}

edited Jan 17 '17 at 14:26

answered Jan 17 '17 at 14:25

davidxxx

125,838
23
214
215

score 0 · Answer 3 · answered Jan 17 '17 at 14:26

0

Your return statement currently does not return anything. Make it return an empty list

answered Jan 17 '17 at 14:26

Jack Bishop

115
1
7

Stephen C · Answer 4 · 2017-01-17T14:36:22.493

This is a better solution:

if (file == null) {
    return list;
}

If you return null then the caller has to deal with the null as a special case. An empty list (which is what list is at that point) can be treated (pretty much) the same way as a non-empty list.

As @Ted Hopp suggests, throwing an exception would be another way to deal with this. It depends on whether you want / need to treat the case where the root directory is empty as exceptional / erroneous ... or as something that doesn't matter.

If you do want this to be "exceptional", it is a good idea.
If not, throwing an exception would be making unnecessary work for code further up the call stack.

Missing return statement error even with return statement at the end of method

4 Answers4