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() + ":	" + x);
            }
            else {
                File[] files = x.listFiles();
                for (int i = 0; i < files.length; i++)
                    queue.enqueue(files[i]);
            }
        }
    }

}