Non-recursive way to get all files in a directory and its subdirectories in Java

Question

I am trying to get a list of all files in a directory and its subdirectories. My current recursive approach is as follows:

private void printFiles(File dir) {
  for (File child : dir.listFiles()) {
    if (child.isDirectory()) {
      printFiles(child);
    } else if (child.isFile()) {
      System.out.println(child.getPath());
    }
  }
}

printFiles(new File("somedir/somedir2"));

However, I was hoping there was a non-recursive way (an existing API call, maybe) of doing this. If not, is this the cleanest way of doing this?

Answer 1

You can always replace a recursive solution with an iterative one by using a stack (for DFS) or a Queue (For BFS):

private void printFiles(File dir) {
  Stack<File> stack = new Stack<File>();
  stack.push(dir);
  while(!stack.isEmpty()) {
    File child = stack.pop();
    if (child.isDirectory()) {
      for(File f : child.listFiles()) stack.push(f);
    } else if (child.isFile()) {
      System.out.println(child.getPath());
    }
  }
}

printFiles(new File("abc/def.ghi"));

Answer 2

Java 8 onward, you can use Files#walk to list out all files and directories recursively in a given directory. Further you can apply the filter like Files::isRegularFile to filter out the directories if you need only regular files.

On the flip side, if you only need to list the given directory but not its sub-directories, you can use the lazy method Files#list which will only give you the files and directories in the given directory. You can again further apply the filter mentioned above.