Chapter 20, Problem 20.18PE

(Directory size) Listing 18.10, DirectorySize.java, gives a recursive method for finding a directory size. Rewrite this method without using recursion. Your program should use a queue to store the subdirectories under a directory. The algorithm can be described as follows:

long getSize(File directory) {

  long size = 0;

  add directory to the queue;

  while (queue is not empty) {

    Remove an item from the queue into t;

    if (t is a file)

      size += t.1ength();

    else

      add all the files and subdirectories under t into the

        queue ;

  }

  return size;

}