RemoteCache should implement size() and isEmpty()

It's dead easy to do this by simply checking the stats returned by the server, i.e.

@Override
public int size()

{ assertRemoteCacheManagerIsStarted(); StatsOperation op = operationsFactory.newStatsOperation(); return Integer.parseInt(((Map<String, String>) op.execute()).get(ServerStatistics.CURRENT_NR_OF_ENTRIES)); }

@Override
public boolean isEmpty()

{ return size() == 0; }