Selector selector = Selector.open()
DatagramChannel channel = DatagramChannel.open(StandardProtocolFamily.INET);
channel.configureBlocking(false);
channel.register(selector, SelectionKey.OP_READ);
while (true) {
    if (selector.select(1000) > 0) { //timeout 1 second
        // process received data
    }
}

channel.join(group, interface);