Exception while using apache lucene for stop words removal -

i using following code stop words removal input text. getting following exception when tokenstream.incrementtoken() runs.

java.lang.illegalstateexception: tokenstream contract violation: reset()/close() call missing, reset() called multiple times, or subclass not call super.reset(). please see javadocs of tokenstream class more information correct consuming workflow. 

code :

public static string removestopwords(string textfile) throws exception {         chararrayset stopwords = englishanalyzer.getdefaultstopset();         tokenstream tokenstream = new standardtokenizer();         tokenstream = new stopfilter(tokenstream, stopwords);         stringbuilder sb = new stringbuilder();         chartermattribute chartermattribute = tokenstream.addattribute(chartermattribute.class);         tokenstream.reset();         while (tokenstream.incrementtoken()) {             string term = chartermattribute.tostring();             sb.append(term + " ");         }         return sb.tostring();     } 

instantiate tokenstream below -

tokenstream tokenstream = new standardanalyzer().tokenstream("field",new stringreader(textfile));