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import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import java.util.function.Predicate;
public class GuardedObject {
//受保护的对象
T obj;
final Lock lock = new ReentrantLock();
final Condition done = lock.newCondition();
final int timeout = 2;
//保存所有GuardedObject
final static Map gos = new ConcurrentHashMap();
//静态方法创建GuardedObject
static GuardedObject create(K key) {
GuardedObject go = new GuardedObject();
gos.put(key, go);
return go;
}
static void fireEvent(K key, T obj) {
GuardedObject go = gos.remove(key);
if (go != null) {
go.onChanged(obj);
}
}
//获取受保护对象
T get(Predicate p) {
lock.lock();
try {
//MESA管程推荐写法
while (!p.test(obj)) {
done.await(timeout,
TimeUnit.SECONDS);
}
} catch (InterruptedException e) {
throw new RuntimeException(e);
} finally {
lock.unlock();
}
//返回非空的受保护对象
return obj;
}
//事件通知方法
void onChanged(T obj) {
lock.lock();
try {
this.obj = obj;
done.signalAll();
} finally {
lock.unlock();
}
}
}