package text;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class MD5 {
   //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"};  
       
     
    public static String generatePassword(String inputString){  
        return encodeByMD5(inputString);  
     }  
       
       
    public static boolean validatePassword(String password, String inputString){  
        if(password.equals(encodeByMD5(inputString))){  
            return true;  
         } else{  
            return false;  
         }  
     }  
     
    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;  
     }  
       
     
    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();  
     }  
       
     
    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];  
     }  
}