用Java实现MD5加密

package james;

import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class MD5 {

	// MD5 加密
	public static String getMD5Str(String str) {
		MessageDigest messageDigest = null;
		try {
			messageDigest = MessageDigest.getInstance("MD5");
			messageDigest.reset();
			messageDigest.update(str.getBytes("UTF-8"));
		} catch (NoSuchAlgorithmException e) {
			e.printStackTrace();
		} catch (UnsupportedEncodingException e) {
			e.printStackTrace();
		}
		byte[] byteArray = messageDigest.digest();
		StringBuffer md5StrBuff = new StringBuffer();
		for (int i = 0; i < byteArray.length; i++) {
			if (Integer.toHexString(0xFF & byteArray[i]).length() == 1)
				md5StrBuff.append("0").append(Integer.toHexString(0xFF & byteArray[i]));
			else
				md5StrBuff.append(Integer.toHexString(0xFF & byteArray[i]));
		}
		return md5StrBuff.toString();
	}

	// MD5 加密
	public static String getMD5(String inStr) {
		MessageDigest md5 = null;
		try {
			md5 = MessageDigest.getInstance("MD5");
		} catch (Exception e) {
			System.out.println(e.toString());
			e.printStackTrace();
			return "";
		}
		char[] charArray = inStr.toCharArray();
		byte[] byteArray = new byte[charArray.length];
		for (int i = 0; i < charArray.length; i++) {
			byteArray[i] = (byte) charArray[i];
		}
		byte[] md5Bytes = md5.digest(byteArray);
		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));
		}
		return hexValue.toString();
	}

	// 可逆的加密算法
	public static String KL(String inStr) {
		char[] a = inStr.toCharArray();
		for (int i = 0; i < a.length; i++) {
			a[i] = (char) (a[i] ^ 't');
		}
		String s = new String(a);
		return s;
	}

	// 解密
	public static String JM(String inStr) {
		char[] a = inStr.toCharArray();
		for (int i = 0; i < a.length; i++) {
			a[i] = (char) (a[i] ^ 't');
		}
		String k = new String(a);
		return k;
	}

	public static void main(String args[]) {
		String s = new String("James");
		System.out.println("原始：" + s);
		System.out.println("MD5后：" + getMD5Str(s));
		System.out.println("MD5后：" + getMD5(s));
		System.out.println("MD5后再加密：" + KL(getMD5(s)));
		System.out.println("解密为MD5后的：" + JM(KL(getMD5(s))));
	}
}