Blacklist strings in an array on android

Question

I have an app that I have made for friends to randomize races for a board game, such that a player gets a randomly selected species every time. I want to include a feature in an update that will allow for a blacklist so that certain races cannot be chosen. What would be the best way to go about this? I'll take any and all advice. Much thanks in advance.

Of note: The array consists of strings of names, and I'd like for this to be persistent for as long as they have the app installed or until they change it.

Edit: Apologies for my lack of clarity. I know generally how I need to do it, but what about saving the settings from the settings menu so that upon closing and reopening, blacklisted races are persistent? Even when the app is closed, upon reopening I'd like for the settings to stay the same. That way next time they play the game (weeks later), assuming their tastes haven't changed, they can go to clicking without blacklisting again.

Answer 1

What you need to do is persist data. You can use two solutions: 1) The SharedPreferences framework for saving key-value pairs without any effort. See here to see how to save a list Store a List or Set in SharedPreferences

2) use SQL database. (custom solution)

In case 1 you would persist the blacklisted strings and in case 2 you would be best to create a table with all strings and have a boolean as to whether its blacklisted or not.

I recommend the shared preferences one since it should take you 5 min to do whereas, unless you are familiar with databases, the database solution will take you a while to work out.

Answer 2

Without any code, it's hard to say for sure how to go about this, because I don't know how you're implementing the rest of the app.

One way I can think of doing this is if you associate an integer with each race, e.g. by using constants:

public static final GIRAFFE = 1;
public static final GOOSE = 2;

Then you could generate random integers to randomly pick each race. If you created a method for the random integer generation, you could then pass certain numbers that would be excluded. You could keep generating a random integer while the integer generated was one of the excluded numbers.

E.g. (Since it's Android I'll code in Java)

// assume min = smallest integer assigned to an animal,  
// and max = largest integer assigned to an animal

public static int randomNumber(int ... exclude)
{
    int random = min + (int)(Math.random() * ((max - min) + 1));
    for (int i = 0; i < exclude.length; i++)
    {
         if (exclude[i] == random)
             random = Min + (int)(Math.random() * ((Max - Min) + 1));
    }
    return random;
}

I'm a little new to StackOverflow, so let me know if this helps.