filemd5info.java

这是一个获取文件MD5码的JAVA程序。可以用于学习JAVA

package com.md5.chen;


import java.io.*;
import java.security.*;

public class FileMD5Info
{
    private static int BUFFER_SIZE = 32 *1024;
    private static String[] hexDigits = {"0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f"};
    private static String PATH;
    
    public static void main(String []args)throws IOException
    {
    	/*
    	
    	String help = "Usage:java MD5Info";
    	help += "'s MD5Info files";
    	if(args.length == 0)
    	{
    	    System.out.println(help);
    	    return ;
    	}
    	
    	for(int i=0;i<args.length;i++)
    	{
    		System.out.println(args[i]+":"+md5(args[i]));
    	}
    	*/
    	
        
    	//读取主目录的路径
		BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
		System.out.println("输入文件夹路径:");
		PATH = reader.readLine();// 将主目录路径保存再PATH中
	

		try
		{
			// PATH=args[0];//以命令行参数为主路径
			System.out.println("path=" + PATH);
			System.out.println("MD5:"+md5(PATH));
			
		} catch (Exception e)
		{
		    e.printStackTrace();
			System.out.println("路径名不合法!");
		}
    }
    
    public static String md5(String f)
    {
         BufferedInputStream file;
         MessageDigest md;
         DigestInputStream in;
         String digestString="";
         
         try
         {
           // 打开文件
           file = new BufferedInputStream(new FileInputStream(f) );
           //创造一个MD5消息
           md = MessageDigest.getInstance("MD5");
           //Filter the file as a DigestInputStream object
           in = new DigestInputStream(file,md);
           int i;
           byte[] buffer = new byte[BUFFER_SIZE];
           
           //读取文件并处理
           do
           {
              i = in.read(buffer,0,BUFFER_SIZE);
           }
           while(i == BUFFER_SIZE)
                 ;
           //Get the final digest and convert it to a String
           md = in.getMessageDigest();
           in.close();
           byte[] digest = md.digest();
           digestString = byteArrayToHexString(digest);
           	  
           
         }
         catch(FileNotFoundException e)
         {
             return f+" not found";
         }
         catch(NoSuchAlgorithmException e)
         {
             return "MD5 not supported.";
         }
         catch(IOException e)
         {
            return "Error reading from "+f+".";
         }
         
         return digestString;
       
    }

    
    
  
      
       
       //Convert a byte to a hexadecimal string
       public static String byteToHexString(byte b)
       {
       	   int n= b;
       	   if(n < 0)
       	   {
       	      n= 256 + n;
       	   }
       	   int d1 = n/16;
       	   int d2 = n%16;
       	   return hexDigits[d1]+hexDigits[d2];
       	
       }
       
       //convert a byte array to a hexadecimal String
       public static String byteArrayToHexString(byte[] b)
       {
       	  String result = "";
       	  for (int i=0;i<b.length;i++)
       	  {
       	     result += byteToHexString(b[i]);
       	  }
       	  return result;
       }
    

}