java判断ipv6的ip 和默认网关在同一网段的函数

可以使用Java的InetAddress类来实现判断IPv6的IP地址和默认网关是否在同一网段的功能，具体代码如下：

import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.util.Enumeration;

public class IPv6Util {
    public static boolean isInSameSubnet(String ip1, String ip2, String subnetMask) throws Exception {
        InetAddress inetAddress1 = InetAddress.getByName(ip1);
        InetAddress inetAddress2 = InetAddress.getByName(ip2);
        InetAddress subnet = InetAddress.getByName(subnetMask);

        if (inetAddress1 instanceof java.net.Inet6Address && inetAddress2 instanceof java.net.Inet6Address && subnet instanceof java.net.Inet6Address) {
            byte[] bytes1 = inetAddress1.getAddress();
            byte[] bytes2 = inetAddress2.getAddress();
            byte[] subnetBytes = subnet.getAddress();

            // 获取接口列表
            Enumeration<NetworkInterface> interfaces = NetworkInterface.getNetworkInterfaces();
            while (interfaces.hasMoreElements()) {
                NetworkInterface ni = interfaces.nextElement();
                Enumeration<InetAddress> addresses = ni.getInetAddresses();
                while (addresses.hasMoreElements()) {
                    InetAddress address = addresses.nextElement();
                    if (address instanceof java.net.Inet6Address) {
                        byte[] interfaceBytes = address.getAddress();
                        if (interfaceBytes.length == 16 && interfaceBytes[0] == bytes1[0] && interfaceBytes[1] == bytes1[1] && interfaceBytes[2] == bytes1[2] && interfaceBytes[3] == bytes1[3] &&
                                interfaceBytes[4] == bytes2[0] && interfaceBytes[5] == bytes2[1] && interfaceBytes[6] == bytes2[2] && interfaceBytes[7] == bytes2[3] &&
                                interfaceBytes[8] == subnetBytes[0] && interfaceBytes[9] == subnetBytes[1] && interfaceBytes[10] == subnetBytes[2] && interfaceBytes[11] == subnetBytes[3]) {
                            return true;
                        }
                    }
                }
            }
        }

        return false;
    }
}

其中，isInSameSubnet函数接收三个参数：需要判断的两个IPv6地址和子网掩码，返回值为一个布尔值，表示这两个IPv6地址是否在同一子网中。

此处的实现方式是通过遍历本地网络接口的方式，获取到每个接口的IPv6地址和子网掩码，然后判断需要判断的两个IPv6地址和子网掩码是否在同一个接口的子网中。如果判断成功，则返回true，否则返回false。