MD5加密（32位，大寫/小寫）

很少說其餘的，MD5加密用於一些數據的保密，列入：密碼等；在這所用的是MD5加密成32位。

32位：（第一種）

public class MD5 {

    // 全局數組

//大寫
//    private final static String[] strDigits = { "0", "1", "2", "3", "4", "5",

//            "6", "7", "8", "9", "A", "B", "C", "D", "E", "F" };

//小寫

//    private final static String[] strDigits = { "0", "1", "2", "3", "4", "5",

//            "6", "7", "8", "9", "a", "b", "c", "d", "e", "f" };

    public MD5() {
    }

    // 返回形式爲數字跟字符串
    private static String byteToArrayString(byte bByte) {
        int iRet = bByte;
        // System.out.println("iRet="+iRet);
        if (iRet < 0) {
            iRet += 256;
        }
        int iD1 = iRet / 16;
        int iD2 = iRet % 16;
        return strDigits[iD1] + strDigits[iD2];
    }

    // 返回形式只爲數字
    private static String byteToNum(byte bByte) {
        int iRet = bByte;
        System.out.println("iRet1=" + iRet);
        if (iRet < 0) {
            iRet += 256;
        }
        return String.valueOf(iRet);
    }

    // 轉換字節數組爲16進制字串
    private static String byteToString(byte[] bByte) {
        StringBuffer sBuffer = new StringBuffer();
        for (int i = 0; i < bByte.length; i++) {
            sBuffer.append(byteToArrayString(bByte[i]));
        }
        return sBuffer.toString();
    }

    public static String GetMD5Code(String strObj) {
        String resultString = null;
        try {
            resultString = new String(strObj);
            MessageDigest md = MessageDigest.getInstance("MD5");
            // md.digest() 該函數返回值爲存放哈希值結果的byte數組
            resultString = byteToString(md.digest(strObj.getBytes()));
        } catch (NoSuchAlgorithmException ex) {
            ex.printStackTrace();
        }
        return resultString;
    }

    public static void main(String[] args) {
        MD5 getMD5 = new MD5();
        System.out.println("MD5的結果："+getMD5.GetMD5Code("qweerretw%$12sde"));
    }
}

（第二種）

public static String stringMD5(String pw) {    try {        MessageDigest messageDigest =MessageDigest.getInstance("MD5");        byte[] inputByteArray = pw.getBytes();        messageDigest.update(inputByteArray);        byte[] resultByteArray = messageDigest.digest();        return byteArrayToHex(resultByteArray);    } catch (NoSuchAlgorithmException e) {        return null;    }}public static String byteArrayToHex(byte[] byteArray) {    char[] hexDigits = {'0','1','2','3','4','5','6','7','8','9', 'a','b','c','d','e','f' }    char[] resultCharArray =new char[byteArray.length * 2];    int index = 0;    for (byte b : byteArray) {        resultCharArray[index++] = hexDigits[b>>> 4 & 0xf];        resultCharArray[index++] = hexDigits[b& 0xf];    }    return new String(resultCharArray);}