Java uses UUID to generate 19 random numbers of pure digits, numbers + letters only not repeat number

/**
 * Created by CC 
 * Generates order number
 * Uuid:db30cc85-3387-4845-87bc-dc390b55b7ea Top 8 + 201508171108900 (YYMMDDHHMMSS )
 * namely: db30cc85201508171108900/Public
class Ordernoutil {

public static  string Getorderno () {
    string orderNo = "";
 UUID uuid = Uuid.randomuuid ();
String Trandno = string.valueof (Math.random () * 9 + 1) * 1000000);
    String SDF = new SimpleDateFormat ("YYYYMMDDHHMMSS"). Format (new Date ());
    OrderNo = uuid.tostring (). substring (0, 8);
    OrderNo = OrderNo + sdf;
    return orderNo;
}

Generate 19 random number of pure digits
public static string Getorderno () {String orderNo = ""; String Trandno = String. ValueOf ((Math. Random () * 9 + 1) * 1000000); String SDF = new SimpleDateFormat ("YYYYMMDDHHMMSS"). Format (new Date ()); OrderNo = trandno.tostring (). substring (0, 4); OrderNo = OrderNo + sdf; return orderNo; }}