public class SumBusinessLogic
{
+ private final Map<String, Long> state;
+
+
public SumBusinessLogic()
{
+ this(new HashMap<>());
}
+ public SumBusinessLogic(Map<String, Long> state)
+ {
+ this.state = state;
+ }
+
+
public synchronized void startSum(String user)
{
+ if (state.containsKey(user))
+ throw new IllegalStateException("Sumation for " + user + " already in progress, state: " + state.get(user));
+
+ state.put(user, 0l);
}
}