Executando programa externo e recuperando a saída (Java)

import java.io.*;
public class Executar {

public static void main(String argv[]) {
try {
String line;
Process p = Runtime.getRuntime().exec (”dir c:“);
BufferedReader input =
new BufferedReader
(new InputStreamReader(p.getInputStream()));
while ((line = input.readLine()) != null) {
System.out.println(line);
}
input.close();
}
catch (Exception err) {
err.printStackTrace();
}
}
}