MD5加密和驗證Java程序

import java.security.MessageDigest;

/**

對密碼進行加密和驗證的程序
*/
public class Password {
/* 十六進制下數字到字符的映射數組 /
 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。

@param inputString
待加密的字符串
@return
*/
public static String createPassword(String inputString) {
 return encodeByMD5(inputString);
}
/**

驗證輸入的密碼是否正確

@param password
真正的密碼（加密后的真密碼）
@param inputString
輸入的字符串
@return
*/
public static boolean authenticatePassword(String password,

 String inputString) {

if (password.equals(encodeByMD5(inputString))) {

 return true;

} else {

 return false;

}
}
/**

對字符串進行MD5編碼

@param originString
@return
*/
private static String encodeByMD5(String originString) {
 if (originString != null) {

 try {
     MessageDigest md = MessageDigest.getInstance("MD5");
     byte[] results = md.digest(originString.getBytes());
     String resultString = byteArrayToHexString(results);
     return resultString.toUpperCase();
 } catch (Exception ex) {
     ex.printStackTrace();
 }

}
 return null;
}
/**

轉換字節數組為16進制字串

@param b
字節數組
@return 十六進制字串
*/
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();
}
/**

將一個字節轉化成16進制形式的字符串

@param b
@return
*/
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 password = Password.createPassword("888888");
 System.out.println("對888888用MD5摘要后的字符串：" + password);
 String inputString = "8888";
 System.out.println("8888與密碼匹配？"

     + Password.authenticatePassword(password, inputString));

inputString = "888888";
 System.out.println("888888與密碼匹配？"

     + Password.authenticatePassword(password, inputString));

}
}</pre>