Throwing NullPointerException & ExceptionInInitializerError

DiscordEventHandlers handlers = new DiscordEventHandlers.Builder().setReadyEventHandler((user) -> {
    this.ready = true;
    DiscordRichPresence.Builder presence = new DiscordRichPresence.Builder("<state>");
    presence.setStartTimestamps(System.currentTimeMillis() / 1000L);
    presence.setDetails("<details>");
    presence.setBigImage("<key>", "<text>");
    presence.setSmallImage("<key>", "<text>");
    DiscordRPC.discordUpdatePresence(presence.build());
}).build();
DiscordRPC.discordInitialize("<ID>", handlers, false); //Throws error here
DiscordRPC.discordRegister("<ID>", "");
while (true) {
    DiscordRPC.discordRunCallbacks();
    if (!this.ready)
        continue;
    DiscordRichPresence.Builder presence = new DiscordRichPresence.Builder("<state>");
    presence.setDetails("<details>");
    DiscordRPC.discordUpdatePresence(presence.build());
}