Android studio Navigation drawer - Expression expected -

i'm trying create tutorial app. i'm getting message saying

expression expected

under

case 2:     activity = new lesson111();     break; 

note - not whole code of main activity. however, problem starts when change

case 2:     fragment = new lesson111();     break; 

to

case 2:     activity = new lesson111();     break; 

here main.activity:

public class navigationactivity extends fragmentactivity {      private drawerlayout mdrawerlayout;     imageview home;     fragment fragment = null;     textview appname;     expandablelistview explistview;     hashmap<string, list<string>> listdatachild;     expandablelistadapter listadapter;     list<string> listdataheader;      @override     protected void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         setcontentview(r.layout.activity_navigation);         home = (imageview)findviewbyid(r.id.home);         home.setonclicklistener(homeonclicklistener);         appname = (textview)findviewbyid(r.id.appname);         setupdrawer();     }      /**      *       * names , icons references build drawer menu...      */     private void setupdrawer() {         mdrawerlayout = (drawerlayout) findviewbyid(r.id.drawer_layout);         mdrawerlayout.setscrimcolor(getresources().getcolor(android.r.color.transparent));         mdrawerlayout.setdrawerlistener(mdrawerlistener);         explistview = (expandablelistview) findviewbyid(r.id.lvexp);         preparelistdata();         listadapter = new expandablelistadapter(this, listdataheader, listdatachild);         // setting list adapter         explistview.setadapter(listadapter);         fragment = new lesson1();         getsupportfragmentmanager().begintransaction().replace(r.id.content_frame, fragment).commit();         mdrawerlayout.closedrawer(explistview);          explistview.setonchildclicklistener(new onchildclicklistener() {             @override             public boolean onchildclick(expandablelistview parent, view v, int groupposition, int childposition, long id) {                 switch (groupposition) {                 case 0:                     switch (childposition) {                     case 0:                         fragment = new lesson1();                         break;                     case 1:                         fragment = new lesson11();                         break;                     case 2:                         activity = new lesson111();                         break;                     default:                         break;                     }                     break; 

my problem solved response. thank you

you havent initialized activity variable. try activity activity = new lesson111(); – onur Çevik