Java面试--String和byte[]之间的转化(MD5加密)

客官°小女子只卖身不卖艺 2021-09-27 07:56 323阅读 0赞

> **面试题：Java如何把byte类型转换成字符串**

**一、常规的String转byte\[\]  
代码分析：**

public static byte[] strToByteArray(String str) {
        if (str == null) {
            return null;
        }
        byte[] byteArray = str.getBytes();
        return byteArray;
    }

**二、常规的byte\[\]转String  
代码分析：**

public static String byteArrayToStr(byte[] byteArray) {
        if (byteArray == null) {
            return null;
        }
        String str = new String(byteArray);
        return str;
    }

**三、byte\[\]转化为十六进制的String  
代码分析：**

private static final String hexDigits[] = {
       "0", "1", "2", "3", "4", "5","6", "7", "8", "9", "a", "b", "c", "d", "e", "f"};
    //单个字节转换成16进制的字符串
    private static String byteToHexString(byte b) {
        int n = b;
        if (n < 0） n += 256;
        int d1 = n / 16;   //取出高4位
        int d2 = n % 16;   //取出低4位
        return hexDigits[d1] + hexDigits[d2];
    }
    //将字节数组转换成16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();
    }
    //测试代码：
    public static void main(String[] args) {
        byte[] b = {
       10,11};
        String s = MD5Util.byteArrayToHexString(b);
        System.out.println(s);
    }
    //运行结果：
    //0a0b

**四、MD5工具类  
代码分析：**

public class  MD5Util {
    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;
        int d1 = n / 16;
        int d2 = n % 16;
        return hexDigits[d1] + hexDigits[d2];
    }
    
    public static void main(String[] args) {
        byte[] b = {
       10,11};
        String s = MD5Util.byteArrayToHexString(b);
    
        String s1 = MD5Util.MD5EncodeUtf8("101112a");
        System.out.println(s1.length());
    }
    //返回大写MD5
    private static String MD5Encode(String origin, String charsetname) {
        String resultString = null;
        try {
            resultString = new String(origin);
            MessageDigest md = MessageDigest.getInstance("MD5");
            if (charsetname == null || "".equals(charsetname))
                resultString = byteArrayToHexString(md.digest(resultString.getBytes()));
            else
                resultString = byteArrayToHexString(md.digest(resultString.getBytes(charsetname)));
        } catch (Exception exception) {
        }
        return resultString.toUpperCase();
    }
    
    public static String MD5EncodeUtf8(String origin) {
        origin = origin + PropertiesUtil.getProperty("password.salt", "");
        return MD5Encode(origin, "utf-8");
    }
    
    
    private static final String hexDigits[] = {
       "0", "1", "2", "3", "4", "5",
            "6", "7", "8", "9", "a", "b", "c", "d", "e", "f"};

--------------------

**Java面试的完整博客目录如下：[Java笔试面试目录][Java]**

> **转载请标明出处，原文地址：[https://blog.csdn.net/weixin\_41835916][https_blog.csdn.net_weixin_41835916] 如果觉得本文对您有帮助，请点击顶支持一下，您的支持是我写作最大的动力，谢谢。  
> ![这里写图片描述][70]**

[Java]: https://blog.csdn.net/weixin_41835916/article/details/81413498
[https_blog.csdn.net_weixin_41835916]: https://blog.csdn.net/weixin_41835916
[70]: /images/20210923/167fa2ed0c554e0abb9eb5d1dd81a103.png