Executar comando do dos

Runtime rt = Runtime.getRuntime();
Process pros = rt.exec("comando msdos ou linux");

import java.io.*;

public class ExecutaComandoNativo 
{
	
	private final String COMANDO_WINDOWS = "cmd";
	
    private Process processoWindows;
    private BufferedReader saidaPadraoWindows;
    private BufferedOutputStream entradaPadraoWindows;
    private BufferedReader saidaErroWindows;
        
    public ExecutaComandoNativo() 
    {
    }
    
    public Process getProcessoWindows() throws IOException
    {
		if(processoWindows == null)
		{
			processoWindows = Runtime.getRuntime().exec(COMANDO_WINDOWS);
		}
		
		return processoWindows;
	}
	
	public BufferedOutputStream getEntradaPadraoWindows() throws IOException
	{
		if(entradaPadraoWindows == null)
		{
			entradaPadraoWindows = new BufferedOutputStream(getProcessoWindows().getOutputStream());
		}
		return entradaPadraoWindows;
	}

	public BufferedReader getSaidaErroWindows() throws IOException
	{
		if(saidaErroWindows == null)
		{
			saidaErroWindows = new BufferedReader(new InputStreamReader(getProcessoWindows().getErrorStream()));
		}
		return saidaErroWindows;
	}

	public BufferedReader getSaidaPadraoWindows() throws IOException
	{
		if(saidaPadraoWindows == null)
		{
			saidaPadraoWindows = new BufferedReader(new InputStreamReader(getProcessoWindows().getInputStream()));
		}
		return saidaPadraoWindows;
	}
	
	public void executarComando(String comando)throws IOException
	{
		getEntradaPadraoWindows().write(comando.getBytes());
		getEntradaPadraoWindows().flush();
		getEntradaPadraoWindows().close();
	}
	
	public void finalizarProcessoWindows()throws Exception
	{

		entradaPadraoWindows = null;
		
		saidaPadraoWindows = null;
		
		saidaErroWindows = null;
		
		processoWindows.destroy();
		processoWindows = null;
	}
	
	public static void main(String[] s)
	{
		ExecutaComandoNativo executaComandoNativo = new ExecutaComandoNativo();
		String FFMPEG = "C:\\ffmpeg\\ffmpeg.exe";
		try
		{
			//String comando = "copy \""+documento.getCaminho()+"\" \""+documento.getCaminhoClearcase()+"\"\n";
			//String comando = "dir c: \n";
			//String comando = "ffmpeg -formats\n";
			//String comando = "ffmpeg \n";
			//String comando = "ffmpeg -i C:\\Joel Luis Carbonera\\Programação - Projetos\\Projetos\\Projetos em Java\\Projeto - Indexador de informações em arquivos multimídia\\Arquivos de teste\\Arquivos de teste  1\\videos\\teste.mpg convertido.mpeg \n";
			
			String arquivoASerVonvertido = "C:\\Arquivos de teste\\videos\\Pixar - Ice Age Extra.mpg";
			String comando = FFMPEG+" -i "+arquivoASerVonvertido+" -f mpeg c:\\conv.mpg\n";
			
			executaComandoNativo.executarComando(comando);
			
			(executaComandoNativo.getProcessoWindows()).waitFor();
			
			
			String saida;
			while((saida = executaComandoNativo.getSaidaPadraoWindows().readLine()) != null)
			{
				System.out.println(saida);
			}
			
			
			while( (saida = executaComandoNativo.getSaidaErroWindows().readLine()) != null )
			{
				System.err.println(saida);
			}
			
			
			/*
			if((executaComandoNativo.getProcessoWindows()).exitValue()!=null)
			{
				executaComandoNativo.finalizarProcessoWindows();
			}
			*/
		}
		catch(Exception ioe)
		{
			System.out.println("Problema 2");
			ioe.printStackTrace();
		}
	}
}