pack() blocks when second thread is running

In the following application (called SystemConsole), the pack() call blocks
until the second thread terminates. Since the second thread shouldn't be
interfering with the event dispatch thread, I don't understand why AWT stops
at this point. (The second thread does run properly.)


import java.awt.*;
import java.io.*;

public class SystemConsole extends Frame {
    private TextArea text;

    public SystemConsole() {
super("System Console");
System.err.println("supered");
text = new TextArea(24, 80);
System.err.println("created");
add("Center", text);
System.err.println("added");
// Application blocks inside of pack() until ReadStdin terminates.
pack();
System.err.println("packed");
show();
    }

    public boolean handleEvent(Event evt) {
System.err.println("frame event " + evt);
if (evt.id == Event.WINDOW_DESTROY) {
System.exit(0);
return true;
}
return false;
    }

    public static void main(String argv[]) {
Thread t = new Thread(new ReadStdin());
t.start();
System.err.println("new thread started");
Frame f = new SystemConsole();
System.err.println("console created");
//t.stop();
//System.err.println("new thread stopped");
    }
}

class ReadStdin implements Runnable {
    public void run() {
System.out.println("test system console");
DataInputStream in = new DataInputStream(System.in);
String line;
try {
while ((line = in.readLine()) != null) {
System.out.println(line);
}
} catch (IOException e) {
System.out.println("IOException: " + e);
}
System.out.println("test done");
    }
}