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The source code
package org.apache.lucene.search.spans;
/**
* Copyright 2004 The Apache Software Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import java.io.IOException;
import java.util.Collection;
import java.util.List;
import java.util.ArrayList;
import java.util.Iterator;
import org.apache.lucene.index.IndexReader;
/** Matches spans which are near one another. One can specify slop, the
* maximum number of intervening unmatched positions, as well as whether
* matches are required to be in-order. */
public class SpanNearQuery extends SpanQuery {
private List clauses;
private int slop;
private boolean inOrder;
private String field;
/** Construct a SpanNearQuery. Matches spans matching a span from each
* clause, with up to slop total unmatched positions between
* them. * When inOrder is true, the spans from each clause
* must be * ordered as in clauses . */
public SpanNearQuery(SpanQuery[] clauses, int slop, boolean inOrder) {
// copy clauses array into an ArrayList
this.clauses = new ArrayList(clauses.length);
for (int i = 0; i < clauses.length; i++) {
SpanQuery clause = clauses[i];
if (i == 0) { // check field
field = clause.getField();
} else if (!clause.getField().equals(field)) {
throw new IllegalArgumentException("Clauses must have same field.");
}
this.clauses.add(clause);
}
this.slop = slop;
this.inOrder = inOrder;
}
/** Return the clauses whose spans are matched. */
public SpanQuery[] getClauses() {
return (SpanQuery[])clauses.toArray(new SpanQuery[clauses.size()]);
}
/** Return the maximum number of intervening unmatched positions permitted.*/
public int getSlop() { return slop; }
/** Return true if matches are required to be in-order.*/
public boolean isInOrder() { return inOrder; }
public String getField() { return field; }
public Collection getTerms() {
Collection terms = new ArrayList();
Iterator i = clauses.iterator();
while (i.hasNext()) {
SpanQuery clause = (SpanQuery)i.next();
terms.addAll(clause.getTerms());
}
return terms;
}
public String toString(String field) {
StringBuffer buffer = new StringBuffer();
buffer.append("spanNear([");
Iterator i = clauses.iterator();
while (i.hasNext()) {
SpanQuery clause = (SpanQuery)i.next();
buffer.append(clause.toString(field));
if (i.hasNext()) {
buffer.append(", ");
}
}
buffer.append("], ");
buffer.append(slop);
buffer.append(", ");
buffer.append(inOrder);
buffer.append(")");
return buffer.toString();
}
public Spans getSpans(final IndexReader reader) throws IOException {
if (clauses.size() == 0) // optimize 0-clause case
return new SpanOrQuery(getClauses()).getSpans(reader);
if (clauses.size() == 1) // optimize 1-clause case
return ((SpanQuery)clauses.get(0)).getSpans(reader);
return new NearSpans(this, reader);
}
}
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