import java.util.HashMap;
import java.util.Map;
+import java.util.Optional;
public class SumBusinessLogic
state.put(user, 0l);
}
+
+ public synchronized Optional<Long> getSum(String user)
+ {
+ return Optional.ofNullable(state.get(user));
+ }
+
+ public synchronized Long endSum(String user)
+ {
+ if (!state.containsKey(user))
+ throw new IllegalStateException("No sumation for " + user + " in progress");
+
+ return state.get(user);
+ }
}