Token Generator Using Threads

Question

I have a class that I am using to generate 10 character alphanumeric 'tokens' (Strings) and writing them to a txt file.

I would like to be able to generate as many as possible as quickly as possible without producing any duplicates. This is what I have so far:

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Random;
public class TokenGenerator {
 public static void main(String[] args) {
 for (;;) {
 getSaltString();
 }
 }
public static void getSaltString() {
 String SALTCHARS = "ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";
 StringBuilder salt = new StringBuilder();
 Random rnd = new Random();
 while (salt.length() < 10) { // length of the random string.
 int index = (int) (rnd.nextFloat() * SALTCHARS.length());
 salt.append(SALTCHARS.charAt(index));
 }
 String saltStr = salt.toString();
 writer(saltStr);
}
public static void writer(String code) {
 try {
 File file = new File("codes.txt");
 PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter(file, true)));
 out.println(code);
 out.close();
 } catch (IOException e) {
 System.out.println("Dead");
 }
 }
}

I was wondering,

A: Is this an efficient way of generating the tokens?

B: How can I call this method using threads to generate them faster

Answer 1

Bug 1

Requirement is 'without producing any duplicates'. You have not exactly implemented this (although the chances of happening are really small)

Bug 2

You have no condition of exiting. The program will run forever, and might have inconsistent behaviour if you terminate it externally.

A: Is this an efficient way of generating the tokens?

It can be more efficient.

• You can keep the File and Writers open instead of opening each time.
• You can reuse the new Random() instead of creating one each time, or..
• ...use int randomNum = ThreadLocalRandom.current().nextInt(min, max + 1);
• You can use a fixed for loop instead of checking the salt.length().

Also use try-with-resources.

B: How can I call this method using threads to generate them faster

As you write to file, this process will finally be I/O bound, so there is probably no real gain from multi-threading.