BaseKeyGenerator.java

public static class BaseKeyGenerator
{
    
    public static void TestBaseKeyGenerator()
    {
        // create five IDs of six, base 62 characters
        for (int i=0; i<5; i++) Console.WriteLine(BaseKeyGenerator.GetBase62(6));
    
        // create five IDs of eight base 36 characters
        for (int i=0; i<5; i++) Console.WriteLine(BaseKeyGenerator.GetBase36(8));
    }
    
    private static char[] _base62chars =
        "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
        .ToCharArray();

    private static Random _random = new Random();

    public static string GetBase62(int length)
    {
        var sb = new StringBuilder(length);

        for (int i=0; i<length; i++)
            sb.Append(_base62chars[_random.Next(62)]);

        return sb.ToString();
    }

    public static string GetBase36(int length)
    {
        var sb = new StringBuilder(length);

        for (int i=0; i<length; i++)
            sb.Append(_base62chars[_random.Next(36)]);

        return sb.ToString();
    }
}