package org.apache.lucene.search;
/**
* 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 org.apache.lucene.index.Term;
import org.apache.lucene.index.TermEnum;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.util.ToStringUtils;
/** A Query that matches documents containing terms with a specified prefix. A PrefixQuery
* is built by QueryParser for input like <code>app*</code>. */
public class PrefixQuery extends Query {
private Term prefix;
/** Constructs a query for terms starting with <code>prefix</code>. */
public PrefixQuery(Term prefix) {
this.prefix = prefix;
}
/** Returns the prefix of this query. */
public Term getPrefix() { return prefix; }
public Query rewrite(IndexReader reader) throws IOException {
BooleanQuery query = new BooleanQuery(true);
TermEnum enumerator = reader.terms(prefix);
try {
String prefixText = prefix.text();
String prefixField = prefix.field();
do {
Term term = enumerator.term();
if (term != null &&
term.text().startsWith(prefixText) &&
term.field() == prefixField) {
TermQuery tq = new TermQuery(term); // found a match
tq.setBoost(getBoost()); // set the boost
query.add(tq, BooleanClause.Occur.SHOULD); // add to query
//System.out.println("added " + term);
} else {
break;
}
} while (enumerator.next());
} finally {
enumerator.close();
}
return query;
}
/** Prints a user-readable version of this query. */
public String toString(String field) {
StringBuffer buffer = new StringBuffer();
if (!prefix.field().equals(field)) {
buffer.append(prefix.field());
buffer.append(":");
}
buffer.append(prefix.text());
buffer.append('*');
buffer.append(ToStringUtils.boost(getBoost()));
return buffer.toString();
}
/** Returns true iff <code>o</code> is equal to this. */
public boolean equals(Object o) {
if (!(o instanceof PrefixQuery))
return false;
PrefixQuery other = (PrefixQuery)o;
return (this.getBoost() == other.getBoost())
&& this.prefix.equals(other.prefix);
}
/** Returns a hash code value for this object.*/
public int hashCode() {
return Float.floatToIntBits(getBoost()) ^ prefix.hashCode() ^ 0x6634D93C;
}
}
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