The hashing function is used to generate random strings of six characters, that can be numbers or upper and lowercase letters. We need to make sure that a string is not already used, but, choosing from 62 characters, we can make about ten billions strings. If we are getting repeated strings, we will output some warnings, and in this case, the solution would be to use longer codes or just start reusing them.

In the sample of code below, we generate the short code of six characters:

public class HystqioUtils {             private static final String CHARSET =                 "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";             public static String generateShortCode() {                  StringBuilder buffer = new StringBuilder();                  for (int i-0; i                        int r = random.nextInt(CHARSET.length());                       buffer.append(CHARSET.charAt(r));                       }             return buffer.toString();             }          }