public Object clone() 
{
    try {
      return super.clone();
    } catch (CloneNotSupportedException e) {
      throw new RuntimeException("Clone not supported: " + e.getMessage());
    }
}

Returns a clone of this query.

 public Query combine(Query[] queries) 
{
    HashSet< Query > uniques = new HashSet< Query >();
    for (int i = 0; i <  queries.length; i++) {
      Query query = queries[i];
      BooleanClause[] clauses = null;
      // check if we can split the query into clauses
      boolean splittable = (query instanceof BooleanQuery);
      if(splittable){
        BooleanQuery bq = (BooleanQuery) query;
        splittable = bq.isCoordDisabled();
        clauses = bq.getClauses();
        for (int j = 0; splittable && j <  clauses.length; j++) {
          splittable = (clauses[j].getOccur() == BooleanClause.Occur.SHOULD);
        }
      }
      if(splittable){
        for (int j = 0; j <  clauses.length; j++) {
          uniques.add(clauses[j].getQuery());
        }
      } else {
        uniques.add(query);
      }
    }
    // optimization: if we have just one query, just return it
    if(uniques.size() == 1){
        return uniques.iterator().next();
    }
    BooleanQuery result = new BooleanQuery(true);
    for (final Query query : uniques)
      result.add(query, BooleanClause.Occur.SHOULD);
    return result;
}

Expert: called when re-writing queries under MultiSearcher. Create a single query suitable for use by all subsearchers (in 1-1 correspondence with queries). This is an optimization of the OR of all queries. We handle the common optimization cases of equal queries and overlapping clauses of boolean OR queries (as generated by MultiTermQuery.rewrite()). Be careful overriding this method as queries[0] determines which method will be called and is not necessarily of the same type as the other queries.

 public Weight createWeight(Searcher searcher) throws IOException 
{
    throw new UnsupportedOperationException();
}

Expert: Constructs an appropriate Weight implementation for this query.

Only implemented by primitive queries, which re-write to themselves.

 public boolean equals(Object obj) 
{
    if (this == obj)
      return true;
    if (obj == null)
      return false;
    if (getClass() != obj.getClass())
      return false;
    Query other = (Query) obj;
    if (Float.floatToIntBits(boost) != Float.floatToIntBits(other.boost))
      return false;
    return true;
}

 public  void extractTerms(Set<Term> terms) 
{
    // needs to be implemented by query subclasses
    throw new UnsupportedOperationException();
}

Expert: adds all terms occurring in this query to the terms set. Only works if this query is in its rewritten form.

 public float getBoost() 
{
 return boost;
}

Gets the boost for this clause. Documents matching this clause will (in addition to the normal weightings) have their score multiplied by b. The boost is 1.0 by default.

 public Similarity getSimilarity(Searcher searcher) 
{
    return searcher.getSimilarity();
}

Expert: Returns the Similarity implementation to be used for this query. Subclasses may override this method to specify their own Similarity implementation, perhaps one that delegates through that of the Searcher. By default the Searcher's Similarity implementation is returned.

 public int hashCode() 
{
    final int prime = 31;
    int result = 1;
    result = prime * result + Float.floatToIntBits(boost);
    return result;
}

 public static Query mergeBooleanQueries(BooleanQuery queries) 
{
    HashSet< BooleanClause > allClauses = new HashSet< BooleanClause >();
    for (BooleanQuery booleanQuery : queries) {
      for (BooleanClause clause : booleanQuery) {
        allClauses.add(clause);
      }
    }
    boolean coordDisabled =
      queries.length==0? false : queries[0].isCoordDisabled();
    BooleanQuery result = new BooleanQuery(coordDisabled);
    for(BooleanClause clause2 : allClauses) {
      result.add(clause2);
    }
    return result;
}

Expert: merges the clauses of a set of BooleanQuery's into a single BooleanQuery.

A utility for use by #combine(Query[]) implementations.

 public Query rewrite(IndexReader reader) throws IOException 
{
    return this;
}

Expert: called to re-write queries into primitive queries. For example, a PrefixQuery will be rewritten into a BooleanQuery that consists of TermQuerys.

 public  void setBoost(float b) 
{
 boost = b;
}

Sets the boost for this query clause to b. Documents matching this clause will (in addition to the normal weightings) have their score multiplied by b.

 public String toString() 
{
    return toString("");
}

Prints a query to a string.

 abstract public String toString(String field)
Prints a query to a string, with field assumed to be the 
default field and omitted.
The representation used is one that is supposed to be readable
by QueryParser . However,
there are the following limitations:

 
If the query was created by the parser, the printed
 representation may not be exactly what was parsed. For example,
 characters that need to be escaped will be represented without
 the required backslash.
Some of the more complicated queries (e.g. span queries)
 don't have a representation that can be parsed by QueryParser.

 public Weight weight(Searcher searcher) throws IOException 
{
    Query query = searcher.rewrite(this);
    Weight weight = query.createWeight(searcher);
    float sum = weight.sumOfSquaredWeights();
    float norm = getSimilarity(searcher).queryNorm(sum);
    if (Float.isInfinite(norm) || Float.isNaN(norm))
      norm = 1.0f;
    weight.normalize(norm);
    return weight;
}

Expert: Constructs and initializes a Weight for a top-level query.