Java tutorial
//package com.java2s; import java.io.File; public class Main { public static long getTotalSizeOfFilesInDir(final File file) { if (file.isFile()) return file.length(); final File[] children = file.listFiles(); long total = 0; if (children != null) for (final File child : children) total += getTotalSizeOfFilesInDir(child); return total; } }