Java - Search for files in a directory

Question

This is supposed to be simple, but I can\'t get it - \"Write a program that searches for a particular file name in a given directory.\" I\'ve found a few examples of a hardc

Answer 1

Using Java 8+ features we can write the code in few lines:

protected static Collection find(String fileName, String searchDirectory) throws IOException {
    try (Stream files = Files.walk(Paths.get(searchDirectory))) {
        return files
                .filter(f -> f.getFileName().toString().equals(fileName))
                .collect(Collectors.toList());

    }
}

Files.walk returns a Stream which is "walking the file tree rooted at" the given searchDirectory. To select the desired files only a filter is applied on the Stream files. It compares the file name of a Path with the given fileName.

Note that the documentation of Files.walk requires

This method must be used within a try-with-resources statement or similar control structure to ensure that the stream's open directories are closed promptly after the stream's operations have completed.

I'm using the try-resource-statement.

---

For advanced searches an alternative is to use a PathMatcher:

protected static Collection find(String searchDirectory, PathMatcher matcher) throws IOException {
    try (Stream files = Files.walk(Paths.get(searchDirectory))) {
        return files
                .filter(matcher::matches)
                .collect(Collectors.toList());

    }
}

An example how to use it to find a certain file:

public static void main(String[] args) throws IOException {
    String searchDirectory = args[0];
    String fileName = args[1];
    PathMatcher matcher = FileSystems.getDefault().getPathMatcher("regex:.*" + fileName);
    Collection find = find(searchDirectory, matcher);
    System.out.println(find);
}

More about it: Oracle Finding Files tutorial