Metodo para executar comando nao funciona

import java.io.*;
 import java.lang.*;
 
 
 public class teste{
 
 public static void main(String args[]){
 
 String dataset =  "breast-w"; 
 String ext =  ".arff";
 
 String nome_dataset = dataset + ext;
 
 
 String foldTest  = dataset +  "-test" + ext;
 String foldTrain = nome_dataset;
 String resultados = dataset + "_result.txt";
 
 String cmdTrain =  "java -cp c:\\weka\\weka.jar weka.classifiers.trees.J48 -v -t " + foldTrain + " -T " + foldTest;
 
  
     try {
         // Execute command
         String command = "dir";
            System.out.println("1");
         Process child = Runtime.getRuntime().exec(command);
        System.out.println("2");
         // Get input stream to read from it
        BufferedReader in = new BufferedReader(child.getInputStream());
        try{
           String linha = "";
           while((linha = in.readLine()) != null){
                 System.out.println(linha);
           }
        }
        catch(Exception e){
              e.printStackTrace();
        }
                     System.out.println("58");
     } catch (IOException e) {
     }
 
 }
 
 }

System.out.println("1");
         Process child = Runtime.getRuntime().exec(command);
        System.out.println("2");