java - 我怎样才能只获得 IPv4 地址

Question

我有以下代码，它应该只获取所有 Activity 接口(interface)的 IPv4 地址，但它仍然在某些计算机上返回 IPv6 地址。

public static List<List> getIpAddress() {
    List<String> ip = new ArrayList<>();
    List<List> ipRefined = new ArrayList<>();
    try {
        Enumeration<NetworkInterface> interfaces = NetworkInterface.getNetworkInterfaces();
        while (interfaces.hasMoreElements()) {
            NetworkInterface iface = interfaces.nextElement();
            if (iface.isLoopback() || !iface.isUp())
                continue;
            Enumeration<InetAddress> addresses = iface.getInetAddresses();
            while(addresses.hasMoreElements()) {
                ip.add(addresses.nextElement().getHostAddress());
            }
        }
    } catch (SocketException e) {
        throw new RuntimeException(e);
    }
    for(int x = 0; x < ip.size(); x++){
        if(ip.get(x).contains("%")){
            try {
                if (ip.get(x + 1).contains(".")) {
                    List<String> tempList = new ArrayList<>();
                    tempList.add(ip.get(x).substring(ip.get(x).indexOf("%") + 1));
                    tempList.add(ip.get(x + 1));
                    ipRefined.add(tempList);
                }
            } catch (IndexOutOfBoundsException ae) {
            }
        }
    }
    return ipRefined;
}

我尝试使用 System.setProperty("java.net.preferIPv4Stack", "true"); 指定仅使用 IPv4，但这只会导致 getIpAddress() 返回一个空列表。我应该如何在不使用字符串操作的情况下获取 Activity 接口(interface)的 IPv4？

编辑:

使用 System.setProperty("java.net.preferIPv4Stack", "true"); 总是导致 getIpAddress() 返回空列表。

Answer 1

来自 InterfaceAddress

This class represents a Network Interface address. In short it's an IP address, a subnet mask and a broadcast address when the address is an IPv4 one. An IP address and a network prefix length in the case of IPv6 address.

这是我的代码:

Enumeration<NetworkInterface> interfaces = NetworkInterface.getNetworkInterfaces();
while (interfaces.hasMoreElements()) {
  NetworkInterface networkInterface = interfaces.nextElement();
  System.out.println(String.format("networkInterface: %s", networkInterface.toString()));

  if (!networkInterface.isUp()) {
    continue;
  }

  for (InterfaceAddress interfaceAddress : networkInterface.getInterfaceAddresses()) {
    int npf = interfaceAddress.getNetworkPrefixLength();
    InetAddress address = interfaceAddress.getAddress();
    InetAddress broadcast = interfaceAddress.getBroadcast();
    if (broadcast == null && npf != 8) {
      System.out.println(String.format("IPv6: %s; Network Prefix Length: %s", address, npf));
    } else {
      System.out.println(String.format("IPv4: %s; Subnet Mask: %s; Broadcast: %s", address, npf, broadcast));
    }
  }
}