无法使用 PathMatcher 和正则表达式获取文件列表

Question

I'm using PathMatcher and SimpleFileVisitor to iterate over directory and find all the files that start only with a certain prefix. However, I can't get any files although there are some files that match my preference.

Example of file required:

Prefix_some_text.csv

Here is the Main code that invokes the call for SimpleFileVisitor class, and it uses regex pattern with the prefix and suppose to find all files starting with the certain pattern:

String directoryAsString = "C:/Users";
String pattern = "Prefix";
SearchFileByWildcard sfbw = new SearchFileByWildcard();
        try {
            List<String> actual = sfbw.searchWithWc(Paths.get(directoryAsString),pattern);
        } catch (IOException e) {
            e.printStackTrace();
        }

The implementation of SearchFileByWildcard class that uses SimpleFileVisitor:

static class SearchFileByWildcard {
    List<String> matchesList = new ArrayList<String>();
    List<String> searchWithWc(Path rootDir, String pattern) throws IOException {
        matchesList.clear();
        FileVisitor<Path> matcherVisitor = new SimpleFileVisitor<Path>() {
            @Override
            public FileVisitResult visitFile(Path file, BasicFileAttributes attribs) throws IOException {
                FileSystem fs = FileSystems.getDefault();
                PathMatcher matcher = fs.getPathMatcher("regex:" + pattern);
                Path name = file.getFileName(); //takes the filename from the full path
                if (matcher.matches(name)) {
                    matchesList.add(name.toString());
                }
                return FileVisitResult.CONTINUE;
            }
        };
        Files.walkFileTree(rootDir, matcherVisitor);
        return matchesList;
    }
}

I'm debating whether to use glob instead of regex? Or maybe something with my regex is flawed.

Answer 1

It seems like the pattern is wrong. It matches only files named "Prefix". Try to change it in String pattern = "Prefix.*";.

Otherwise you can scan for files which name starts by the string "Prefix".

String name = file.getFileName().toString();
if (name.startsWith(pattern)) {
    matchesList.add(name);
}