算法Sedgewick第四版-第1章基础-025-用队列实现unix下的Directory命令

 package algorithms.util;

 /******************************************************************************
  *  Compilation:  javac Directory.java
  *  Execution:    java Directory directory-name
  *  Dependencies: Queue.java StdOut.java
  *
  *  Prints out all of the files in the given directory and any
  *  subdirectories in level-order by using a queue. Also prints
  *  out their file sizes in bytes.
  *
  *  % java Directory .
  *
  ******************************************************************************/

 import java.io.File;

 import algorithms.ADT.Queue;

 public class Directory { 

     public static void main(String[] args) {
         Queue<File> queue = new Queue<File>();
         File root = new File(args[0]);     // root directory
         if (!root.exists()) {
             StdOut.println(args[0] + " does not exist");
             return;
         }

         queue.enqueue(root);
         while (!queue.isEmpty()) {
             File x = queue.dequeue();
             if (!x.isDirectory()) {
                 StdOut.println(x.length() + ":\t" + x);
             }
             else {
                 File[] files = x.listFiles();
                 for (int i = 0; i < files.length; i++)
                     queue.enqueue(files[i]);
             }
         }
     }

 }