hadoop - Err :"The type Reducer Context.Value Iterator is not visible" in override run() method in reducer -

i wanted add header in reducer class.so overrided run method in reducer , added header described below .

but getting error:

"cannot perform instanceof check against parameterized type reducecontext.valueiterator. use form reducecontext.valueiterator instead since further generic type information erased @ runtime type reducecontext.valueiterator not visible."

any appreciated.thanks in advance.

@ override public void run(context context) throws ioexception, interruptedexception {     setup(context);     column = new text("college") ;     values = new text("firstname" + "\t" + "lastname") ;     context.write(column, values);     try     {         while (context.nextkey())         {             reduce(context.getcurrentkey(), context.getvalues(), context);             // if store used, reset             iterator<intwritable> iter = context.getvalues().iterator();             if(iter instanceof reducecontext.valueiterator)             {                 ((reducecontext.valueiterator<intwritable>)iter).resetbackupstore();                     }         }     }         {         cleanup(context);     } }