Lucene: How to add Hits to ArrayList

Question

I'm trying add Hits to List() (to populate the results on web pages) this way:

List<ScoreDoc> results = null;

if (hits.scoreDocs.length != 0) {
  for(ScoreDoc scoreDoc : hits.scoreDocs) { 
    results.add(scoreDoc);
  }
}

and it reports:

Exception in thread "main" java.lang.NullPointerException
at _test.Searcher.search(Searcher.java:68)
at _test.Searcher.main(Searcher.java:80)

for the results.add(scoreDoc); line.

What I'm doing wrong?

Answer 1

results is null . You will have to create a List before adding items (for example use an ArrayList ).

List<ScoreDoc> results = new ArrayList<ScoreDoc>();