MapIdField { public Object get(String mapId) { return mappedObjects.get(mapId); } MapIdField(); void put(String mapId, Object value); void remove(String mapId); Object get(String mapId); boolean containsMapId(String mapId);  }
@Test public void testGet() { mapIdField.put(null, "nullMapId"); mapIdField.put("aMapId", "aMapIdValue"); assertEquals("nullMapId", mapIdField.get(null)); assertEquals("aMapIdValue", mapIdField.get("aMapId")); }