Mega Code Archive
Wait() and notify() must only be issued inside a synchronized block
<![CDATA[
public class WaitComm {
public static void main(String args[]) {
WFlagSend s = new WFlagSend();
WFlagRec r = new WFlagRec(s);
Thread st = new Thread(s);
Thread rt = new Thread(r);
rt.setDaemon(true);
st.start();
rt.start();
try {
st.join();
while (s.isValid) {
Thread.sleep(100);
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
class WFlagSend implements Runnable {
volatile int theValue;
boolean isValid;
public void run() {
for (int i = 0; i < 5; i++) {
synchronized (this) {
while (isValid) {
try {
this.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
theValue = (int) (Math.random() * 256);
System.out.println("sending " + theValue);
synchronized (this) {
isValid = true;
this.notify();
}
}
}
}
class WFlagRec implements Runnable {
WFlagSend theSender;
public WFlagRec(WFlagSend sender) {
theSender = sender;
}
public void run() {
while (true) {
synchronized (theSender) {
while (!theSender.isValid) {
try {
theSender.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
System.out.println("received " + theSender.theValue);
synchronized (theSender) {
theSender.isValid = false;
theSender.notify();
}
}
}
}
]]>