Java - Ayuda Validacion IP

package pmovi;

import java.io.BufferedReader;

import java.io.InputStreamReader;

import java.util.ArrayList;

/**

 *

 * @author viche

 */

import java.io.BufferedReader;

import java.io.InputStreamReader;

import java.util.ArrayList;

public class PMovi

{

    // method for finding the ping statics of website 

    static void commands(ArrayList<String> commandList)

                                           throws Exception

    {

        // creating the sub process, execute system command 

        ProcessBuilder build = new ProcessBuilder(commandList);

        Process process = build.start();

        // to read the output 

        BufferedReader input = new BufferedReader(new InputStreamReader

                                   (process.getInputStream()));

        BufferedReader Error = new BufferedReader(new InputStreamReader

                                   (process.getErrorStream()));

        String s = null;

        System.out.println("Standard output: ");

        while((s = input.readLine()) != null)

        {

            System.out.println(s);

        }

        System.out.println("error (if any): ");

        while((s = Error.readLine()) != null)

        {

            System.out.println(s);

        }

    }

    // Driver method 

    public static void main(String args[]) throws Exception

    {

        int i;

        // creating list for commands 

        for (i=20;i<100;i++){

        ArrayList<String> commandList = new ArrayList<String>();

        commandList.add("ping");

        // can be replaced by IP 

        commandList.add("31.13.90."+i);

        PMovi.commands(commandList);

        }

        i=20;

    }

}