java MD5

import java.security.MessageDigest;  
/**  
 * 对密码进行加密和验证的类 
 */  
public class CipherUtil{  
     
    //十六进制下数字到字符的映射数组  
    private final static String[] hexDigits = {"0", "1", "2", "3", "4",  
        "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f"};  
     
    /** * 把inputString加密     */  
    public static String generatePassword(String inputString){  
       return encodeByMD5(inputString);  
    }  
      
      /** 
       * 验证输入的密码是否正确 
     * @param password    加密后的密码 
     * @param inputString    输入的字符串 
     * @return    验证结果，TRUE:正确 FALSE:错误 
     */  
   public static boolean validatePassword(String password, String inputString){  
       if(password.equals(encodeByMD5(inputString))){  
            return true;  
       } else{  
           return false;  
       }  
   }  
    /**  对字符串进行MD5加密     */  
    private static String encodeByMD5(String originString){  
        if (originString != null){  
            try{  
               //创建具有指定算法名称的信息摘要  
               MessageDigest md = MessageDigest.getInstance("MD5");  
               //使用指定的字节数组对摘要进行最后更新，然后完成摘要计算  
               byte[] results = md.digest(originString.getBytes());  
               //将得到的字节数组变成字符串返回  
               String resultString = byteArrayToHexString(results);  
               return resultString.toUpperCase();  
          } catch(Exception ex){  
                ex.printStackTrace();  
           }  
        }  
        return null;  
   }  
      
    /**  
    * 转换字节数组为十六进制字符串 
     * @param     字节数组 
     * @return    十六进制字符串 
     */  
   private static String byteArrayToHexString(byte[] b){  
       StringBuffer resultSb = new StringBuffer();  
        for (int i = 0; i < b.length; i++){  
            resultSb.append(byteToHexString(b[i]));  
       }  
       return resultSb.toString();  
   }  
      
    /** 将一个字节转化成十六进制形式的字符串     */  
    private 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];  
    }  
    public static void main(String[] args) {  
    	       String pwd1="abc";  
    	       String pwd2="";  
    	       String pwd3="1234";
    	       CipherUtil cipher = new CipherUtil();  
    	        System.out.println("未加密的密码:"+pwd1);  
    	       //将123加密  
    	        pwd2 = cipher.generatePassword(pwd1);  
    	       System.out.println("加密后的密码:"+pwd2);  
    	          
    	       System.out.print("验证密码是否下确:");  
    	       if(cipher.validatePassword(pwd2, pwd3)) {  
    	            System.out.println("正确");  
    	        }  
    	       else {  
    	            System.out.println("错误");  
    	       }  
    	   } 
}