Jre 1.5 waitfor hangs windows xp if output more than 17 lines

Question

I have seen many postings on the "waitfor" part of an external process. I am too having issues with it. For some reason when there is more than 17 lines of output, "waitfor" hangs. I am executing a simple external command to prove the point. I run the command c:\rundir.bat. All this program does is an "echo hello" multiple times (I alter the number of times to find the threshold).
Any ideas?
Code snipit:
Command is an array of 3
cmd[0] = "c:\windows\system32\cmd.exe"
cmd[1] = "/C"
cmd[2] = "c:\rundir.bat"
p = Runtime.getRuntime().exec(cmd);
rc = p.waitFor(); // Hangs forever if more than 17 lines of output.
if (rc != 0) {
success = false;
br = new BufferedReader(new InputStreamReader(p.getErrorStream()));
else {
success = true;
br = new BufferedReader(new InputStreamReader(p.getInputStream()));
}

Answer 1

1) Search these forums. This problem has been asked over and over again.
2) Read the entire System.exec() and java.lang.Process javadoc. The situation you need to prevent is well-documented.
Briefly put: the error and output streams of the external process must be timely read; failure to do so when executing a process which writes to either or both of these streams can cause deadlock, since writing to a stream may block and the operating system provides limited buffer space for these streams. You will need to use multiple threads.