MD5实现加密解密

import java.security.MessageDigest; 
 
public class MD5Util { 
     
    // MD5加密。32位的。 
    public static String md5ToSecret(String source) { 
        MessageDigest md5 = null; 
        try { 
            md5 = MessageDigest.getInstance("MD5"); 
        } catch (Exception e) { 
            System.out.println(e.toString()); 
            e.printStackTrace(); 
            return ""; 
        } 
        char[] charArray = source.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 md5Encrypt(String inStr) { 
        // String s = new 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; 
    } 
 
    // 加密后解密 
    public static String md5Decrypt(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 = "123456"; 
        System.out.println("原字符串："  + s); 
        System.out.println("MD5加密之后："  + md5ToSecret(s)); 
        System.out.println("再加密："  + md5Encrypt(md5ToSecret(s))); 
        System.out.println("解密之后："  + md5Decrypt(md5Encrypt(md5ToSecret(s)))); 
    } 
}