线程同步与互斥（死锁的避免）

import java.security.MessageDigest;
public class Dxt_SMSMD5{
public final static String MD5(String s) {
char hexdigits[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd','e', 'f'};

try {
byte[] strTemp = s.getBytes();
MessageDigest mdTemp = MessageDigest.getInstance("MD5");
mdTemp.update(strTemp);
byte[] md = mdTemp.digest();
int j = md.length;
char str[] = new char[j * 2];
int k = 0;
for (int i = 0; i < j; i++) {
byte byte0 = md[i];
str[k++] = hexdigits[byte0 >>> 4 & 0xf];
str[k++] = hexdigits[byte0 & 0xf];
}
return new String(str);
}
catch (Exception e) {
return null;
}
}

public static void main(String[] args) {
//MD5_Test aa = new MD5_Test();
System.out.print(Dxt_SMSMD5.MD5("123456"));
}
}