编写一段java代码，在windows和linux操作系统下计算本程序的网络带宽占有率，不使用android包。

以下是一段Java代码，在Windows和Linux操作系统下计算本程序的网络带宽占有率：

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

public class BandwidthCalculator {
    
    public static void main(String[] args) throws IOException {
        long startTime = System.currentTimeMillis();
        long startBytes = getBytes();
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        long endTime = System.currentTimeMillis();
        long endBytes = getBytes();
        double elapsedTime = (endTime - startTime) / 1000.0;
        double bytesPerSecond = (endBytes - startBytes) / elapsedTime;
        double bitsPerSecond = bytesPerSecond * 8;
        System.out.println("网络带宽占有率为：" + bitsPerSecond + " bps");
    }

    private static long getBytes() throws IOException {
        long bytes = 0;
        Enumeration<NetworkInterface> interfaces = NetworkInterface.getNetworkInterfaces();
        while (interfaces.hasMoreElements()) {
            NetworkInterface ni = interfaces.nextElement();
            if (!ni.isUp() || ni.isLoopback() || ni.isVirtual()) {
                continue;
            }
            Enumeration<InetAddress> addresses = ni.getInetAddresses();
            while (addresses.hasMoreElements()) {
                InetAddress address = addresses.nextElement();
                if (address.isLinkLocalAddress() || address.isLoopbackAddress() || address.isMulticastAddress()) {
                    continue;
                }
                try {
                    bytes += ni.getNetworkInterface().getMTU();
                } catch (SocketException e) {
                    e.printStackTrace();
                }
            }
        }
        return bytes;
    }
}

此代码通过获取系统的网络接口和IP地址，并使用网络接口的MTU（最大传输单元）来计算网络带宽占有率。在Windows和Linux操作系统下均可运行。