A me questo funziona

codice:
public class writeOutput {
  
  public writeOutput() {
    try {
      Runtime r = Runtime.getRuntime();
      Process p = r.exec("cmd /k dir \"C:\\*.*\" > C:\\dir.txt");
    }
    catch (Exception e) {
      System.out.print(e.toString());
    }
  }
  
  public static void main (String[] args) {
    writeOutput wo = new writeOutput();    
  }
}
Magari ti aiuta.