public class AlarmClock {
private static final int MAX_CAPACITY = 10;
private static final int UNUSED = -1;
private static final int NOROOM = -1;
private Sleeper[] sleepers = new Sleeper[MAX_CAPACITY];
private long[] sleepFor = new long[MAX_CAPACITY];
public AlarmClock () {
for (int i = 0; i < MAX_CAPACITY; i++)
sleepFor[i] = UNUSED;
}
public synchronized boolean letMeSleepFor(Sleeper s,
long time) {
int index = findNextSlot();
if (index == NOROOM) {
return false;
} else {
sleepers[index] = s;
sleepFor[index] = time;
new AlarmThread(index).start();
return true;
}
}
private synchronized int findNextSlot() {
for (int i = 0; i < MAX_CAPACITY; i++) {
if (sleepFor[i] == UNUSED)
return i;
}
return NOROOM;
}
private synchronized void wakeUpSleeper(int sleeperIndex) {
sleepers[sleeperIndex].wakeUp();
sleepers[sleeperIndex] = null;
sleepFor[sleeperIndex] = UNUSED;
}
private class AlarmThread extends Thread {
int mySleeper;
AlarmThread(int sleeperIndex) {
super();
mySleeper = sleeperIndex;
}
public void run() {
try {
sleep(sleepFor[mySleeper]);
} catch (InterruptedException e) {}
wakeUpSleeper(mySleeper);
}
}
}
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