JAVA对字符串进行32位MD5加密的实践

public static void main(String[] args) {
    String s ="202111012231046012000000111101705104827";
    for (int i = 0; i <50 ; i++) {
        System.out.println( EncodeByMD5(s).toUpperCase()+"   长度"+EncodeByMD5(s).toUpperCase().length());
    }
}

/**
 * 对字符串进行32位MD5加密
 * @param str
 * @return
 */
public static String EncodeByMD5(String str) {
    try {
        // 生成一个MD5加密计算摘要
        MessageDigest md = MessageDigest.getInstance("MD5");
        // 计算md5函数
        md.update(str.getBytes("UTF-8"));
        // digest()最后确定返回md5 hash值，返回值为8为字符串。因为md5 hash值是16位的hex值，实际上就是8位的字符
        // BigInteger函数则将8位的字符串转换成16位hex值，用字符串来表示；得到字符串形式的hash值
        String md5=new BigInteger(1, md.digest()).toString(16);
        //BigInteger会把0省略掉，需补全至32位
        return fillMD5(md5);
    } catch (Exception e) {
        throw new RuntimeException("MD5加密错误:"+e.getMessage(),e);
    }
}

private static String fillMD5(String md5){
    //如果不够32位则回调自身补零，最后返回32位长度的签名
    return md5.length()==32?md5:fillMD5("0"+md5);
}

package com.kuang.jiami;

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

public class MD5Util {
    //待加密的密码
    public static String password = "202111012231046012000000111101705104829";

    public static void main(String args[]) {
        //结果字符串
        String result = "";
        try {
            MessageDigest md = MessageDigest.getInstance("MD5");
            md.update(password.getBytes());
            byte b[] = md.digest();
            int i;
            StringBuffer buf = new StringBuffer("");
            for (int offset = 0; offset < b.length; offset++) {
                i = b[offset];
                if (i < 0)
                    i += 256;
                if (i < 16)
                    buf.append("0");
                buf.append(Integer.toHexString(i));
            }
            result = buf.toString();
            System.out.println("MD5(" + password + ",32小写) = " + result);
            System.out.println("MD5(" + password + ",32大写) = " + result.toUpperCase());
            System.out.println("++++++++++++++++++++++++各位大哥借过+++++++++++++++++++++++");
            System.out.println("MD5(" + password + ",16小写) = " + buf.toString().substring(8, 24));
            System.out.println("MD5(" + password + ",16大写) = " + buf.toString().substring(8, 24).toUpperCase());
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        }
    }
}

package com.kuang.jiami;

import java.security.MessageDigest;


public class MD5Helper {

    public static String encrypt32(String encryptStr) {
        MessageDigest md5;
        try {
            md5 = MessageDigest.getInstance("MD5");
            byte[] md5Bytes = md5.digest(encryptStr.getBytes());
            StringBuffer hexValue = new StringBuffer();
            for (int i = 0; i < md5Bytes.length; i++) {
                int val = ((int) md5Bytes[i]) & 0xff;
                if (val < 16)
                    hexValue.append("0");
                hexValue.append(Integer.toHexString(val));
            }
            encryptStr = hexValue.toString();
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
        return encryptStr;
    }
    
    public static String encrypt16(String encryptStr) {
        return encrypt32(encryptStr).substring(8, 24);
    }

    public static void main(String[] args) {
        String encryptStr = "202111012231046012000000111101705104829";
        System.out.println(MD5Helper.encrypt32(encryptStr).toUpperCase());
        System.out.println(MD5Helper.encrypt16(encryptStr).toUpperCase());
    }
}