HackerRank之Java MD5

MD5 (Message-Digest algorithm 5) is a widely-used cryptographic hash function with a -bit hash value. Here are some common uses for MD5:

• To store a one-way hash of a password.
• To provide some assurance that a transferred file has arrived intact.

MD5 is one in a series of message digest algorithms designed by Professor Ronald Rivest of MIT (Rivest, 1994); however, the security of MD5 has been severely compromised, most infamously by the Flame malware in 2012. The CMU Software Engineering Institute essentially considers MD5 to be "cryptographically broken and unsuitable for further use".

Given an alphanumeric string, , denoting a password, compute and print its MD5 encryption value.

Answer

import java.io.*;
import java.util.*;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;


public class Solution {

    // 全局数组
    private final static String[] strDigits = { "0", "1", "2", "3", "4", "5",
            "6", "7", "8", "9", "a", "b", "c", "d", "e", "f" };

    public Solution() {
    }

    // 返回形式为数字跟字符串
    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];
    }

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

    // 转换字节数组为16进制字串
    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() 该函数返回值为存放哈希值结果的byte数组
            resultString = byteToString(md.digest(strObj.getBytes()));
        } catch (NoSuchAlgorithmException ex) {
            ex.printStackTrace();
        }
        return resultString;
    }

    public static void main(String[] args) {
        Solution getMD5 = new Solution();
        Scanner scan=new Scanner(System.in);
        String str=scan.nextLine();
        scan.close();
        System.out.println(getMD5.GetMD5Code(str));
    }
}