//: FlagComm.java

public class FlagComm {
	public static void main(String[] args) {
		FlagSend s = new FlagSend();
		FlagRec r = new FlagRec(s);
		Thread st = new Thread(s);
		Thread rt = new Thread(r);
		rt.setDaemon(true);
		st.start();
		rt.start();
		try {
			st.join();		//	for Windows
			while ( s.isValid ) {
				Thread.sleep(100);
			}
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
	}
}

class FlagSend implements Runnable {
	volatile int theValue;
	volatile boolean isValid;
	
	public void run() {
		for ( int i=0; i<5; i++ ) {
			while ( isValid ) {
				Thread.yield();
			}
			theValue = (int)(Math.random()*256);
			System.out.println("sending "+theValue);
			isValid = true;
		}
	}
}

class FlagRec implements Runnable {
	FlagSend theSender;
	
	public FlagRec(FlagSend sender) {
		theSender = sender;
	}
	
	public void run() {
		while ( true ) {
			while ( !theSender.isValid ) {
				Thread.yield();
			}
			System.out.println("received "+theSender.theValue);
			theSender.isValid = false;
		}
	}
}