Così modificato ti stampa tutto
codice:
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;


/**
 * @author Zero-2
 *
 *12-giu-2005 20.12.50
 */
public class TestProcess {
       
    
    public static int exec(String pArguments[]) throws IOException {
        class ProcessOutputPrinter implements Runnable {
            private InputStream ivIn;
     
            public ProcessOutputPrinter(InputStream pIn) {
                ivIn = pIn;
            }
     
            public void run() {
                try {
                    InputStreamReader isr = new InputStreamReader(ivIn);
                    BufferedReader br = new BufferedReader(isr);
                    String line=null;
                    while ( (line = br.readLine()) != null)
                        System.out.println(line);    
                    } catch (IOException ioe)
                      {
                        ioe.printStackTrace();  
                      }
                
            }
        };
     

        Process tProcess = Runtime.getRuntime().exec(pArguments);
     
        
        Thread tOutPrinter = new Thread(new ProcessOutputPrinter(tProcess.getInputStream()));
        tOutPrinter.start();
     
        
        Thread tErrPrinter = new Thread(new ProcessOutputPrinter(tProcess.getErrorStream()));
        tErrPrinter.start();
     
        
        try {
            tProcess.waitFor();
            tOutPrinter.join();
            tErrPrinter.join();
        }
        catch(InterruptedException e) {
        }
     
        
        return tProcess.exitValue();
    }
    public static void main(String[] args) throws IOException {
        
        TestProcess.exec(new String[]{"cmd.exe","/C","dir","d:\\"});
    }

}