public IpAddress.Version version() {
        return address.version();
    }
@Test
    public void testVersion() {
        IpPrefix ipPrefix;

        // IPv4
        ipPrefix = IpPrefix.valueOf("0.0.0.0/0");
        assertThat(ipPrefix.version(), is(IpAddress.Version.INET));

        // IPv6
        ipPrefix = IpPrefix.valueOf("::/0");
        assertThat(ipPrefix.version(), is(IpAddress.Version.INET6));
    }