TokenService.java

import org.apache.commons.lang3.RandomStringUtils;

public class TokenService {

    public String createToken(int playbackPosition) {
        String suffix = RandomStringUtils.randomAlphanumeric(16);
        return String.valueOf(playbackPosition) + ":" + suffix;
    }

    public int tokenToPlaybackIndex(String token) {
        String positionStr = token.split(":")[0];
        return Integer.valueOf(positionStr);
    }
}