Java NIO Search file in a directory

Question

I want to search a file(without knowing the full name) in a specific directory using Java NIO and glob.

public static void match(String glob, String location) throws IOException {

        final PathMatcher pathMatcher = FileSystems.getDefault().getPathMatcher(
                glob);

        Files.walkFileTree(Paths.get(location), new SimpleFileVisitor<Path>() {

            @Override
            public FileVisitResult visitFile(Path path,
                    BasicFileAttributes attrs) throws IOException {
                if (pathMatcher.matches(path)) {
                    System.out.println(path);
                }
                return FileVisitResult.CONTINUE;
            }
        });
    }

Reading some tutorial I did this. I just want to return string if I find(first) file with given glob String.

if (pathMatcher.matches(path)) {
    return path.toString();
}

Answer 1

There are two things to be changed:

To "find(first) file with given glob String" you need to finish walking the tree if you encounter the file, thus if a match is given. And you need to store the matching path as result. The result of Files.walkFileTree itself is the "the starting file" (JavaDoc). That's a Path pointing to the location.

public static String match(String glob, String location) throws IOException {
    StringBuilder result = new StringBuilder();
    PathMatcher pathMatcher = FileSystems.getDefault().getPathMatcher(glob);
    Files.walkFileTree(Paths.get(location), new SimpleFileVisitor<Path>() {

        @Override
        public FileVisitResult visitFile(Path path, BasicFileAttributes attrs) throws IOException {
            if (pathMatcher.matches(path)) {
                result.append(path.toString());
                return FileVisitResult.TERMINATE;
            }
            return FileVisitResult.CONTINUE;
        }
    });

    return result.toString();
}

If there is no match then the resulting String is empty.

EDIT:
Using Files.walk we can implement the search with less code still using a glob expression based matcher:

public static Optional<Path> match(String glob, String location) throws IOException {
    PathMatcher pathMatcher = FileSystems.getDefault().getPathMatcher(glob);
    return Files.walk(Paths.get(location)).filter(pathMatcher::matches).findFirst();
}

The Optional as result shows that there may be no match.