feat(core/filter): add field and getter for last received item count

src/main/java/de/hftstuttgart/unifiedticketing/core/Filter.java

@@ -21,6 +21,7 @@ public abstract class Filter<T extends Ticket, F extends Filter<?,?>>
 {
     private static Logger logger = Logging.getLogger(Filter.class.getName());
 
+    protected int lastReceivedItemCount;
     protected Map<String, Object> setFilters;// = new HashMap<>();
 
     protected enum FilterNames
@@ -45,6 +46,22 @@ public abstract class Filter<T extends Ticket, F extends Filter<?,?>>
             this.getClass().getSimpleName()
         ));
         setFilters = new HashMap<>();
+
+        lastReceivedItemCount = -1;
+    }
+
+    /**
+     * Counter how many items received on last {@link #get()} call.
+     *
+     * As local filtering can lower the items delivered from {@link #get()},
+     * you can't check that no more pages are available comparing the delivered item
+     * count with your set page size.<br>
+     *
+     * @return item count received from external Ticketsystem on last call of {@link #get()}
+     */
+    public int getLastReceivedItemCount()
+    {
+        return lastReceivedItemCount;
     }
 
     /**