public class Solution {


    public static List<String> getFileTree(String root) throws IOException {

        List<String> result = new ArrayList<>();
        List<File> files = new ArrayList<>();

        files.add(new File(root));

        for(File xx : files)
        {
            File current = xx;
            if(current.isDirectory())
            {

                for(File f : current.listFiles())
                {
                    files.add(f);
                }
            }
            if(current.isFile())
            {
                result.add(current.getAbsolutePath());
            }
        }

        return result;
    }




    public static void main(String[] args) {
        List<String> fileList = null;
        try {
            fileList = getFileTree("C:\\path");
        } catch (IOException e) {
            e.printStackTrace();
        }
        for (String filePath : fileList)
            System.out.println(filePath);

    }
    }