public class ConnectNetWork {

public static void main(String[] args) throws Exception {
String adslTitle = getConnectName();
String adslName = "************";
String adslPsw = "*******";

connAdsl(adslTitle, adslName, adslPsw);
Thread.sleep(1000);
disconectAdsl(adslTitle);
Thread.sleep(1000);
connAdsl(adslTitle, adslName, adslPsw); // 再连，分配一个新的IP
}

private static String executeCmd(String str) throws Exception {
Process p = Runtime.getRuntime().exec("cmd /c " + str);
StringBuilder sb = new StringBuilder();
BufferedReader br = new BufferedReader(new InputStreamReader(
p.getInputStream(), "gbk"));

String line=null;
while ((line = br.readLine()) != null) {
sb.append(line + "\n");
}
p.destroy();
return sb.toString();
}

private static boolean connAdsl(String adslTitle, String adslName,
String adslPsw) throws Exception {

String adslCmd = "rasdial " + adslTitle + " " + adslName + " "
+ adslPsw;
String tempCmd = executeCmd(adslCmd);

// 判断连接是否成功
if (tempCmd.indexOf("已连接") > 0 || tempCmd.indexOf("已经连接") > 0) {
System.out.println("已成功建立连接.");
return true;
} else {
System.err.println(tempCmd);
return false;
}
}

private static boolean disconectAdsl(String adslTitle) throws Exception {
String cutAdsl = "rasdial " + adslTitle + " /disconnect";
String result = executeCmd(cutAdsl);

if (result.indexOf("没有连接") != -1) {
System.err.println(adslTitle + "连接不存在!");
return false;
} else {
System.out.println("连接已断开");
return true;
}
}

private static String getConnectName() throws Exception {
String reponse = executeCmd("ipconfig /all");
String temp ="描述. . . . . . . . . . . . . . . :";
int begin = reponse.indexOf(temp)+temp.length();
int last = begin+5;
return reponse.substring(begin,last);//返回名称
}
}