JAVA 检测网络是否为连通状态 ping

要用java检测网络资源是否可用，我们可以采用以下两种方法：
一种方法是调用ping命令，
如：
Process process= Runtime.getRuntime().exec("ping 192.168.0.5");
InputStreamReader return = new InputStreamReader(process.getInputStream());
LineNumberReader returnData = new LineNumberReader (return);

String line="";
while((line=returnData.readLine())!=null){
System.out.println(line);
}
通用对返回数据进行分析，来探测网络资源的可用性；
这种方法有一个缺点：就是许多网络资源是不允许被ping的，从而针对这类资源无法探测。

(2008-07-28记)

Dos中的ping 命令能很方便的检测网络是否为连通状态.但是在java中,一直没有找到好的方法检来测网络是否为连通状态.无奈之余,想出了如下方法:

package  com.roadway.edserver.util;

import  java.awt.Toolkit;
import  java.io.InputStream;
import  java.net.HttpURLConnection;
import  java.net.URL;
/** */ /**
 * @Description:本类开启一个线程检测网络是否连通
 * @Author : 惠万鹏
 * @Time :2008-1-10
 */
public   class  NetworkManagement  implements  Runnable  {
    private int htmlCodeSize;
    private int sleepMillisecond;
    private int sleepMillisecondWhenNetWorkUnLinked;
    private boolean isSpontaneousNotice;
    private static boolean networkIsLinked;
    private Thread thread = new Thread(this);
    private Toolkit toolkit;
    private String[] urls;

    public NetworkManagement() {
        this.urls = new String[]{"http://www.baidu.com", "http://www.google.cn"};
        this.htmlCodeSize = 50;
        this.sleepMillisecond = 5000;
        this.sleepMillisecondWhenNetWorkUnLinked = 10000;
        this.toolkit = Toolkit.getDefaultToolkit();
        thread.start();
    }
    public void setURLs(String[] urls) {
        if (urls != null && urls.length > 0) {
            this.urls = urls;
        }
    }
    public void setHtmlCodeSize(int htmlCodeSize) {
        if (htmlCodeSize > 0) {
            this.htmlCodeSize = htmlCodeSize;
        }
    }
    public void isSpontaneousNotice(boolean isSpontaneousNotice) {
        this.isSpontaneousNotice = isSpontaneousNotice;
    }
    public void setSleepMillisecont(int sleepMillisecont) {
        if (sleepMillisecont > 100) {
            this.sleepMillisecond = sleepMillisecont;
        }
    }
    public void setSleepMillisecondWhenNetWorkUnLinked(int sleepMillisecont) {
        if (sleepMillisecont > 100) {
            this.sleepMillisecondWhenNetWorkUnLinked = sleepMillisecont;
        }
    }
    public static boolean IsNetWordLinking() {
        return NetworkManagement.networkIsLinked;
    }

    public void run() {
        while (true) {
            try {
                this.isNetWorkLinked();
                if (!NetworkManagement.networkIsLinked) {
                    this.isPrintMessage(this.isSpontaneousNotice);
                    Thread.sleep(this.sleepMillisecondWhenNetWorkUnLinked);
                }
                System.out.println(NetworkManagement.IsNetWordLinking());
                Thread.sleep(this.sleepMillisecond);
            } catch (Exception e) {
            }
        }
    }

    private boolean canGetHtmlCode(String httpUrl) {
        String htmlCode = "";
        try {
            InputStream in;
            URL url = new java.net.URL(httpUrl);
            HttpURLConnection connection = (HttpURLConnection) url
                    .openConnection();
            connection = (HttpURLConnection) url.openConnection();
            connection.setRequestProperty("User-Agent", "Mozilla/4.0");
            connection.connect();
            in = connection.getInputStream();
            byte[] buffer = new byte[this.htmlCodeSize];
            in.read(buffer);
            htmlCode = new String(buffer);
        } catch (Exception e) {
        }
        if (htmlCode == null || htmlCode.equals("")) {
            return false;
        }
        return true;
    }

    private void isNetWorkLinked() {
        boolean tempIsNetWorkLinked = false;
        for (int urlsCount = 0; urlsCount < this.urls.length; urlsCount++) {
            if (this.canGetHtmlCode(this.urls[urlsCount])) {
                tempIsNetWorkLinked = true;
                break;
            }
        }
        NetworkManagement.networkIsLinked = tempIsNetWorkLinked;
    }
    private void isPrintMessage(boolean isPrint) {
        if (isPrint) {
            toolkit.beep();
            StringBuffer message = new StringBuffer();
            message.append("------------->");
            message.append("网络中断, ");
            message.append(this.sleepMillisecondWhenNetWorkUnLinked);
            message.append(" 毫秒后再次检测!<-------------");
            System.out.println(message.toString());
        }

    }
    public static void main(String[] args) {
        NetworkManagement n = new NetworkManagement();
        n.isSpontaneousNotice(true);
    }
}