内网IP的范围
Class A: 10.0.0.0 到 10.255.255.255
Class B: 172.16.0.0 到 172.31.255.255
Class C: 192.168.0.0 到 192.168.255.255

public class IpChecker {

    private static final Pattern PRIVATE_IP_PATTERN = Pattern.compile(
            "^(10\\.([0-9]{1,3}\\.){2}[0-9]{1,3})|" +
                    "(172\\.(1[6-9]|2[0-9]|3[01])\\.([0-9]{1,3}\\.){1}[0-9]{1,3})|" +
                    "(192\\.168\\.([0-9]{1,3}\\.){1}[0-9]{1,3})$"
    );

    public static boolean isPrivateIP(String ip) {
        return PRIVATE_IP_PATTERN.matcher(ip).matches();
    }

}