JAVA获取子网掩码源代码,查看了jdk以后，知道可以通过NetworkInterface、InterfaceAddress这两个类来实现，可以获得子网掩码前缀，然后通过运算就能得到子网掩码，要说明的是，我计算掩码的方法很土但是很好用，代码也很容易看的懂，还有一个要说明的是，我是xp系统，没有安装ipv6协议.

public class SubnetMask {

/**

* @param args

*/

public static String getSubnetMask(){

int prefix=0;

int[] ipSplit=new int[4];

String subnetMask=null;

InetAddress localMachine=null;

try {

localMachine=InetAddress.getLocalHost();

} catch (UnknownHostException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

NetworkInterface netCard=null;

try {

netCard=NetworkInterface.getByInetAddress(localMachine);

} catch (SocketException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

List localInterface=null;

localInterface=netCard.getInterfaceAddresses();

Iterator iterator=null;

iterator=localInterface.iterator();

while(iterator.hasNext()){

InterfaceAddress temp=null;

temp=iterator.next();

prefix=temp.getNetworkPrefixLength();

}

int index=0;

int split=0;

int remainder=0;

split=prefix/8;

remainder=prefix%8;

while(index

ipSplit[index]=255;

index++;

}

if(remainder==1)

ipSplit[index]=128;

if(remainder==2)

ipSplit[index]=192;

if(remainder==3)

ipSplit[index]=224;

if(remainder==4)

ipSplit[index]=240;

if(remainder==5)

ipSplit[index]=248;

if(remainder==6)

ipSplit[index]=252;

if(remainder==7)

ipSplit[index]=254;

index++;

while(index

ipSplit[index]=0;

index++;

}

subnetMask=String.valueOf(ipSplit[0])+"."+String.valueOf(ipSplit[1])+"."+String.valueOf(ipSplit[2])+"."+String.valueOf(ipSplit[3]);

return subnetMask;

}

public static void main(String[] args) {

// TODO Auto-generated method stub

String subnetMask=getSubnetMask();

System.out.println(subnetMask);

}

}