How to call an Activity from Java step? | Pega Interview Questions

HashStringMap activityKeys = new HashStringMap();
activityKeys.putString("pxObjClass", "Rule-Obj-Activity");
activityKeys.putString("pyClassName", workclass);
activityKeys.putString("pyActivityName", "HistoryAndAttachments" );
tools.doActivity(activityKeys , workpage, tools.getParameterPage() );