How do I iterate through the files in a directory in Java?

Question

I need to get a list of all the files in a directory, including files in all the sub-directories. What is the standard way to accomplish directory iteration with Java?

Answer 1

You can use File#isDirectory() to test if the given file (path) is a directory. If this is true, then you just call the same method again with its File#listFiles() outcome. This is called recursion.

Here's a basic kickoff example.

public static void main(String... args) {
    File[] files = new File("C:/").listFiles();
    showFiles(files);
}

public static void showFiles(File[] files) {
    for (File file : files) {
        if (file.isDirectory()) {
            System.out.println("Directory: " + file.getName());
            showFiles(file.listFiles()); // Calls same method again.
        } else {
            System.out.println("File: " + file.getName());
        }
    }
}

Note that this is sensitive to StackOverflowError when the tree is deeper than the JVM's stack can hold. You may want to use an iterative approach or tail-recursion instead, but that's another subject ;)