Arduino Sends Old Data Through Serial - arduino

Question

I think my problem would best be explained with an example. Here is some Arduino Code:
void setup() {
Serial.begin(9600);
}
void loop() {
Serial.println(millis());
delay(1);
}
...and here is the output:
Now, those numbers at the beginning aren't just your regular old first-bytes-of-serial-data-are-always-messed-up numbers. Those numbers are left over from the last time I opened the serial monitor. How do I know this? Because I counted how many seconds had gone by since I last opened the serial monitor, and it all matched up.
So here's the big questioroonie,
How do I make this stop? It's breaking my java program that's supposed to read data from the Arduino's current "run instance"(I don't know the correct term), and not the last one.

Answer 1

There is nothing wrong with your Arduino. Remember, the USB connection is not a real RS-232 serial interface, it's simulated through USB. And that USB connection is controlled by a chip with its own buffer.
Bad news is, nothing you can do if you're using the USB cable to carry your RS-232 signals, other than to send some "filler characters" to purge the buffer. Too many buffers everywhere :) Send some terminal emulation commands like "clear the screen" and "form feed" etc. to empty the pipeline of stuff in the buffer.
Which reminds me -- we should all quit using the crummy Arduino serial monitor and be vocal about it. Instead, use TeraTerm or Putty or any other good-quality terminal emulator of your choice.
Or connect with real RS232 and an adapter and cable. My development machine has three serial ports, but that's what I do. Often computers today don't even have one handy.