通过文件的md5值快速比较两个文件

import java.applet.*;   
import java.io.*;   
import java.security.*;   
  
public class HashFile {   
    public static char[] hexChar = {'0', '1', '2', '3',   
                                   '4', '5', '6', '7',   
                                   '8', '9', 'a', 'b',   
                                   'c', 'd', 'e', 'f'};   
    public static void main(String[] args) throws  
            Exception {   
        String fileName = "D:\\programs\\Foxmail.rar";   
        String hashType = "MD5";   
        System.out.println(hashType + " == " +   
                           getHash(fileName, hashType));   
        hashType = "SHA1";   
        System.out.println(hashType + " == " +   
                           getHash(fileName, hashType));   
        hashType = "SHA-256";   
        System.out.println(hashType + " == " +   
                           getHash(fileName, hashType));   
        hashType = "SHA-384";   
        System.out.println(hashType + " == " +   
                           getHash(fileName, hashType));   
        hashType = "SHA-512";   
        System.out.println(hashType + " == " +   
                           getHash(fileName, hashType));   
  
    }   
  
    public static String getHash(String fileName, String hashType) throws  
            Exception {   
        InputStream fis;   
        fis = new FileInputStream(fileName);   
        byte[] buffer = new byte[1024];   
        MessageDigest md5 = MessageDigest.getInstance(hashType);   
        int numRead = 0;   
        while ((numRead = fis.read(buffer)) > 0) {   
            md5.update(buffer, 0, numRead);   
        }   
        fis.close();   
        return toHexString(md5.digest());   
    }   
  
    public static String toHexString(byte[] b) {   
        StringBuilder sb = new StringBuilder(b.length * 2);   
        for (int i = 0; i < b.length; i++) {   
            sb.append(hexChar[(b[i] & 0xf0) >>> 4]);   
            sb.append(hexChar[b[i] & 0x0f]);   
        }   
        return sb.toString();   
    }   
}