java - My interface when triggered get NullPointerException -

i try toast message interface. if app not connection internet, want show toast message , i'm wanting java interfaces.

this motheractivity.java. file implement toastmessagges.toastmessaggecallback

   public class motheractivity extends actionbaractivity implements toastmessagges.toastmessaggecallback {          toastmessagges toastmessagges;          @override         protected void onstart() {             super.onstart();          }          @override         protected void oncreate(bundle savedinstancestate) {             super.oncreate(savedinstancestate);             setcontentview(r.layout.activity_mother);              toastmessagges      = new toastmessagges();              appstarter();         }          private void appstarter(){              boolean checkinternet   = internetcontrol.checkinternetconnection( getapplicationcontext() );             if( checkinternet ) {                 toastmessagges.show_toast_messagge();             }             else {              }          }          @override         public void longtoastmessagge() {             toast.maketext(getapplicationcontext(), "hello world", toast.length_long).show();   } } 

this toastmessagges.java file.

public class toastmessagges {      toastmessaggecallback toastmessaggecallback;     public void show_toast_messagge(){         toastmessaggecallback.longtoastmessagge();     }       public static interface toastmessaggecallback {         public void longtoastmessagge();     } } 

when start app. nullpointerexception error.

caused by: java.lang.nullpointerexception             @ com.medyasef.bulenttirasnewapp.bulenttiras.functions.toastmessagges.show_toast_messagge(toastmessagges.java:22)             @ com.medyasef.bulenttirasnewapp.bulenttiras.motheractivity.appstarter(motheractivity.java:36)             @ com.medyasef.bulenttirasnewapp.bulenttiras.motheractivity.oncreate(motheractivity.java:29) 

toastmessagges.java:22

toastmessaggecallback.longtoastmessagge(); 

sorry bad english. please help. thank you.

you haven't initialized toastmessaggecallback toastmessaggecallback.

to this, write

toastmessaggecallback toastmessaggecallback = new toastmessaggecallback(){      public void longtoastmessagge(){         // add toasting code here     }  }; 

this make object implementing interface (called "anonymous class"). of course, toastmessaggecallback should in method longtoastmessagge, add desired code there.