MI have a program that starts with for loop and it spins for 10 times, and one loop lasts one second. I need to handle a signal (CTRL+C) and while handling it, it should do it's own for loop, and after it stops, then I should return to the main loop. I've managed to do almost everything above, but the loops don't execute separately. They do it parallel. Hope you can help... thanks :)
BTW, my code is:
import sun.misc.Signal;
import sun.misc.SignalHandler;
public class MySig {
public static void shhh(int s){ //s -> seconds :)
s = s*1000;
try{
Thread.sleep(s);
}catch(InterruptedException e){
System.out.println("Uh-oh :(");
}
}
public static void main(String[] args){
Signal.handle(new Signal("INT"), new SignalHandler () {
public void handle(Signal sig) {
for(int i=0; i<5; i++){
System.out.println("+");
shhh(1);
}
}
});
for(int i=0; i<10; i++) {
shhh(1);
System.out.println(i+"/10");
}
}
}
Right, according to the docs, SignalHandler is executed in a separate thread:
...when the VM receives a signal, the special C signal handler creates a
new thread (at priority Thread.MAX_PRIORITY) to run the registered
Java signal handler..
If you want to stop your main loop while the handler is executing, you can add a locking mechanism, something like this:
private static final ReentrantLock lock = new ReentrantLock(true);
private static AtomicInteger signalCount = new AtomicInteger(0);
public static void shhh(int s) { // s -> seconds :)
s = s * 1000;
try {
System.out.println(Thread.currentThread().getName() + " sleeping for "
+ s + "s...");
Thread.sleep(s);
} catch (InterruptedException e) {
System.out.println("Uh-oh :(");
}
}
public static void main(String[] args) throws Exception {
Signal.handle(new Signal("INT"), new SignalHandler() {
public void handle(Signal sig) {
// increment the signal counter
signalCount.incrementAndGet();
// Acquire lock and do all work
lock.lock();
try {
for (int i = 0; i < 5; i++) {
System.out.println("+");
shhh(1);
}
} finally {
// decrement signal counter and unlock
signalCount.decrementAndGet();
lock.unlock();
}
}
});
int i = 0;
while (i < 10) {
try {
lock.lock();
// go back to wait mode if signals have arrived
if (signalCount.get() > 0)
continue;
System.out.println(i + "/10");
shhh(1);
i++;
} finally {
// release lock after each unit of work to allow handler to jump in
lock.unlock();
}
}
}
There might be a better locking strategy.