A query can be boosted to increase it's score relative to other subqueries. This is done by wrapping it with a BoostQuery
Query lessRelevantQuery = new TermQuery(new Term("fieldname", "ipsum"));
//Five times as interesting
Query highlyRelevantQuery = new BoostQuery(
new TermQuery(new Term("fieldname", "lorem")),
5.0f);
BooleanQuery query = new BooleanQuery.Builder()
.add(lessRelevantQuery, BooleanClause.Occur.SHOULD)
.add(highlyRelevantQuery, BooleanClause.Occur.SHOULD)
.build();