产生16位的强随机数

public static String getGUID() {
   StringBuilder uid = new StringBuilder();
   //产生16位的强随机数
   Random rd = new SecureRandom();
   for (int i = 0; i < 16; i++) {
      //产生0-2的3位随机数
      int type = rd.nextInt(3);
      switch (type){
         case 0:
            //0-9的随机数
            uid.append(rd.nextInt(10));
            break;
         case 1:
            //ASCII在65-90之间为大写,获取大写随机
            uid.append((char)(rd.nextInt(25)+65));
            break;
         case 2:
            //ASCII在97-122之间为小写，获取小写随机
            uid.append((char)(rd.nextInt(25)+97));
            break;
         default:
            break;
      }
   }
   return uid.toString();
}

 

//16位纯数字随机数
public static String getGUIDNUM() {
   StringBuilder uid = new StringBuilder();
   /*Date date = new Date();
   SimpleDateFormat sdf = new SimpleDateFormat("hhmmss");
   uid.append(sdf.format(date));
   int lenght = uid.length();*/
   int lenght = 0 ;
   Random rd = new SecureRandom();
   if(lenght<16){
      for(int i=0;i<16-lenght;i++){
         uid.append(rd.nextInt(10));
      }
   }
   return uid.toString();
}