在JAVA中如何用 MessageDigest实现MD5的加密

import java.security.MessageDigest;import java.security.NoSuchAlgorithmException;public class MessageDigestUtil {        public static void main(String[] args) {        String txt = "123";        byte[] bys = digest(txt.getBytes(), MessageDigestType.MD5);        System.out.println(ByteUtil.bytes2Hex(bys));    }            private static byte[] digest(byte[] bys, MessageDigestType type) {        if(bys == null || bys.length == 0 || type == null) {            throw new IllegalArgumentException("argument is invalid!");        }        MessageDigest m = null;        try {            m = MessageDigest.getInstance(type.getAlgorithms());        } catch (NoSuchAlgorithmException e) {        }        m.update(bys);        return m.digest();    }   }class MessageDigestType {    private String algorithms;        private MessageDigestType(String algorithms) {        this.algorithms = algorithms;    }        public final static MessageDigestType MD2 = new MessageDigestType("MD2");    public final static MessageDigestType MD5 = new MessageDigestType("MD5");    public final static MessageDigestType SHA1 = new MessageDigestType("SHA-1");    public final static MessageDigestType SHA256 = new MessageDigestType("SHA-256");    public final static MessageDigestType SHA384 = new MessageDigestType("SHA-384");    public final static MessageDigestType SHA512 = new MessageDigestType("SHA-512");        public String getAlgorithms() {        return algorithms;    }}class ByteUtil {    private final static char[] HEX = "0123456789abcdef".toCharArray();        /**     * 将字节数组转成 16 进制的字符串来表示，每个字节采用两个字符表表示     *      * @param bys       需要转换成 16 进制的字节数组     * @return     */    public static String bytes2Hex(byte[] bys) {        char[] chs = new char[bys.length * 2];        for(int i = 0, offset = 0; i < bys.length; i++) {            chs[offset++] = HEX[bys[i] >> 4 & 0xf];            chs[offset++] = HEX[bys[i] & 0xf];        }        return new String(chs);    }}