1:  

   2:     //打印指定目录中的.java文件

   3:     private static void fileFilter()

   4:     {

   5:         File f = new File("d:\\code\\java_blog_code");

   6:  

   7:         //FilenameFilter用来设置过滤器

   8:         String[] s = f.list(new FilenameFilter()

   9:         {

  10:             public boolean accept(File dir,String name)

  11:             {

  12:                 if(name.endsWith(".java"))

  13:                     return true;

  14:                 else

  15:                     return false;

  16:             }

  17:         });

  18:  

  19:         for(String ss : s)

  20:         {

  21:             System.out.println(ss);

  22:         }

  23:     }

   1: //根据层级打印制表符

   2: private static void printLevel(int level)

   3: {

   4:     for(int i = 0 ; i < level ; i ++)

   5:     {

   6:         System.out.print("\t");

   7:     }

   8: }

   9:  

  10: //利用递归，分层次打印指定目录的文件

  11: private static void showFiles(File dir,int level)

  12: {

  13:     //打印目录名

  14:     printLevel(level);

  15:     System.out.println(dir.getName());

  16:  

  17:     File[] files = dir.listFiles();

  18:     

  19:     for(File f : files)

  20:     {

  21:         if(f.isDirectory())

  22:             //如果是目录，传入方法进行递归

  23:             showFiles(f,level+1);

  24:         else

  25:         {

  26:             //打印文件列表

  27:             printLevel(level+1);

  28:             System.out.println(f.getName());

  29:         }

  30:     }

  31: }

   1: import java.io.*;

   2: import java.util.*;

   3:  

   4: /*

   5: 模拟限制程序运行次数

   6: */

   7: class PropertiesDemo 

   8: {

   9:     public static void main(String[] args) throws IOException

  10:     {

  11:         

  12:         Properties prop = new Properties();

  13:  

  14:         //导入info.txt的字节流信息

  15:         prop.load(new FileInputStream("info.txt"));

  16:         

  17:         //获取程序运行次数

  18:         String times = prop.getProperty("times");

  19:     

  20:         //如果第一次运行，则设置次数为1

  21:         if(times == null)

  22:             prop.setProperty("times","1");

  23:         //如果次数大于5次，则打印缴费信息，退出程序

  24:         else if(times.compareTo("4") > 0)

  25:         {

  26:             System.out.println("times greater than 5!please donate money!");

  27:             System.exit(0);

  28:         }

  29:         //程序在允许运行次数范围内，获取次数，并加1

  30:         else

  31:         {

  32:             prop.setProperty("times",""+(Integer.parseInt(times)+1));

  33:         }

  34:         

  35:         //将设置的新次数写入到info文件中

  36:         prop.store(new FileOutputStream("info.txt"),"times");

  37:         

  38:         //程序主题，可无视

  39:         for(int i = 0 ; i < 10 ; i ++)

  40:         {

  41:             System.out.println("i = "+i);

  42:         }

  43:         

  44:         

  45:     }

  46:  

  47:  

  48: }