区别:  MD5加密:
    加密时通过原字符串加密成另一串字符串

    解密时需要原加密字符串进行重新加密比较两次加密结果是否一致
  RSA加密:
    加密时通过原字符串生成密钥对(公钥+私钥)

    解密时通过公钥和私钥进行解密,解密出原字符串进行比较是否一致
个人观点:
  RSA加密略比MD5加密牛逼一点点
  但凡事都有好坏 MD5加密执行效率比RSA快

废话不多说上栗子:  MD5加密:

package cn.news.util;

import java.security.MessageDigest;

/**
 * 
 * @author: 房上的猫
 * 
 * @time: 2018年5月14日 下午8:04:44
 * 
 * @博客地址: https://www.cnblogs.com/lsy131479/
 *
 */
public class MD5 {
    private static String MD(String s) {
        try {
            MessageDigest md = MessageDigest.getInstance("MD5");
            //md.update(s.getBytes("utf-8"));
            byte[] bytes = md.digest(s.getBytes("utf-8"));
            return toHex(bytes);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    private static String toHex(byte[] bytes) {

        final char[] HEX_DIGITS = "0123456789ABCDEF".toCharArray();
        StringBuilder ret = new StringBuilder(bytes.length * 2);
        for (int i = 0; i < bytes.length; i++) {
            ret.append(HEX_DIGITS[(bytes[i] >> 4) &amp; 0x0f]);
            ret.append(HEX_DIGITS[bytes[i] &amp; 0x0f]);
        }
        return ret.toString();
    }

    public static void main(String[] args) {

        System.out.println(MD("hello word"));
    }
}

结果:
图片描述

RSA加密与解密:

package cn.news.util;

import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.util.Base64;

import javax.crypto.Cipher;

/**
 * 
 * @author: 房上的猫
 * 
 * @time: 2018年5月14日 下午7:56:12
 * 
 * @博客地址: https://www.cnblogs.com/lsy131479/
 *
 */
public class RSA {
    public static String data = "hello world";

    public static void main(String[] args) throws Exception {
        // TODO Auto-generated method stub

        KeyPair keyPair = genKeyPair(1024);

        // 获取公钥,并以base64格式打印出来
        PublicKey publicKey = keyPair.getPublic();
        System.out.println("公钥:" + new String(Base64.getEncoder().encode(publicKey.getEncoded())));

        // 获取私钥,并以base64格式打印出来
        PrivateKey privateKey = keyPair.getPrivate();
        System.out.println("私钥:" + new String(Base64.getEncoder().encode(privateKey.getEncoded())));

        // 公钥加密
        byte[] encryptedBytes = encrypt(data.getBytes(), publicKey);
        System.out.println("加密后:" + new String(encryptedBytes));

        // 私钥解密
        byte[] decryptedBytes = decrypt(encryptedBytes, privateKey);
        System.out.println("解密后:" + new String(decryptedBytes));
    }

    // 生成密钥对
    public static KeyPair genKeyPair(int keyLength) throws Exception {
        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
        keyPairGenerator.initialize(1024);
        return keyPairGenerator.generateKeyPair();
    }

    // 公钥加密
    public static byte[] encrypt(byte[] content, PublicKey publicKey) throws Exception {
        Cipher cipher = Cipher.getInstance("RSA");// java默认"RSA"="RSA/ECB/PKCS1Padding"
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
        return cipher.doFinal(content);
    }

    // 私钥解密
    public static byte[] decrypt(byte[] content, PrivateKey privateKey) throws Exception {
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.DECRYPT_MODE, privateKey);
        return cipher.doFinal(content);
    }
}

运行结果:
图片描述