The setEnablePositionIncrements method is not clear whether we should set to true or false.

From the source code of StopFilter.java:

public final class StopFilter extends TokenFilter {
private final CharArraySet stopWords;
private boolean enablePositionIncrements = false;

One can see that enablePositionIncrements is set, by default, to false, which means don't preserve the "holes".

So, are you suggesting to set explicitly to false, even thou the default is already set to false? Or am I missing any bit?

"true" means the position will be incremented to reflect the holes left behind when stopwords are removed.

The defaulting is complicated...

In 3.0.1, StopFilter's ctor requires that you pass in enablePositionIncrements, so there's no default at the class level. However StopFilter exposes a static getEnablePositionIncrementsVersionDefault, which returns true when version is >= 2.9. Analyzers that create a StopFilter uses this to get the version-dependent default.

This explains why the AnalyzerUtils.displayTokensWithPositions works with position incrementation without the need to set the variable to true.

It is all much clear now. Thank you!