java中可以通过调用ping命令来判断网络是否连接正常

  
import java.io.BufferedReader;  
import java.io.IOException;  
import java.io.InputStream;  
import java.io.InputStreamReader;  
  
/** 
 * 判断网络连接状况. 
 * @author nagsh 
 * 
 */  
public class NetState {  
  
    public boolean isConnect(){  
        boolean connect = false;  
        Runtime runtime = Runtime.getRuntime();  
        Process process;  
        try {  
            process = runtime.exec("ping " + "www.baidu.com");  
            InputStream is = process.getInputStream();   
            InputStreamReader isr = new InputStreamReader(is);   
            BufferedReader br = new BufferedReader(isr);   
            String line = null;   
            StringBuffer sb = new StringBuffer();   
            while ((line = br.readLine()) != null) {   
                sb.append(line);   
            }   
            System.out.println("返回值为:"+sb);    
            is.close();   
            isr.close();   
            br.close();   
  
            if (null != sb && !sb.toString().equals("")) {   
                String logString = "";   
                if (sb.toString().indexOf("TTL") > 0) {   
                    // 网络畅通    
                    connect = true;  
                } else {   
                    // 网络不畅通    
                    connect = false;  
                }   
            }   
        } catch (IOException e) {  
            e.printStackTrace();  
        }   
        return connect;  
    }  
      
    public static void main(String[] args) {  
        NetState netState = new NetState();  
        System.out.println(netState.isConnect());  
  
    }  
  
}