Java networkinterface.isVirtual() 方法总是返回值是 false？

Question

什么情况下返回值为true？

谢谢大家!

public class Test1 {

    public static void main(String[] args) {
        try {
            Enumeration<NetworkInterface> networkInterface = NetworkInterface
                    .getNetworkInterfaces();
            while (networkInterface.hasMoreElements()) {
                NetworkInterface eachNetworkInterface = networkInterface
                        .nextElement();
                System.out.println(eachNetworkInterface.getName() + " "
                        + eachNetworkInterface.isVirtual());
            }
        } catch (SocketException e) {
            e.printStackTrace();
        }

    }

}

打印结果全部错误!为什么？如何打印 true？

Answer 1

根据javadocs :

Returns whether this interface is a virtual interface (also called subinterface). Virtual interfaces are, on some systems, interfaces created as a child of a physical interface and given different settings (like address or MTU). Usually the name of the interface will the name of the parent followed by a colon (:) and a number identifying the child since there can be several virtual interfaces attached to a single physical interface.

如果您得到的结果均为false，则仅意味着您的系统中没有创建任何子接口(interface)。