Runtime.exec() won't work

Question

Hi all,
i've got a program that i want to via a java program,
in ms-dos, the programma is called by:
mace2 -n9 -p -m10 -c <puzzle.in> puzzle.outBut in my java program if I use:
Process mace = Runtime.getRuntime().exec("mace2 -n9 -p -m10 -c <puzzle.in> puzzle.out");the program gets called, but never ends properly, and the java
program halts.
Anything wrong? Thanks in advance.

Answer 1

You can't read, write and run in the same thread - this was tested using the group example and -n4; using -n9 would take a long time.
import java.io.*;
class Piper implements Runnable {
  InputStream in;
  OutputStream out;
  Piper (InputStream in, OutputStream out) {
    this.in = new BufferedInputStream(in);
    this.out = new BufferedOutputStream(out);
  public void run () {
    try {
      try {
        try {
          for (int i; (i = in.read()) != -1; ) {
            out.write((byte)i);
        } finally {
          in.close();
        out.flush();
      } finally {
        out.close();
    } catch (IOException ex) {
      ex.printStackTrace();
public class CallMace {
  static final String pathToMace = "<whatever>\Otter33-Win32\\bin\\";
  static void runMace (String inFile, String outFile) {
    try {
      Process p = Runtime.getRuntime().exec(pathToMace + "mace2 -n9 -p -m10 -c");
      Thread tIn = new Thread(new Piper(new FileInputStream(inFile), p.getOutputStream()));
      Thread tOut = new Thread(new Piper(p.getInputStream(), new FileOutputStream(outFile)));
      tIn.start();                              
      tOut.start();                              
      p.waitFor();
      tIn.join();
      tOut.join();
    } catch (Exception ex) {
      ex.printStackTrace();
  public static void main (String...args) {
    runMace(args[0], args[1]);
}Pete