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Lucene example source code file (TermRangeTermEnum.java)

This example Lucene source code file (TermRangeTermEnum.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Lucene tags/keywords

collator, collator, filteredtermenum, io, ioexception, override, override, string, string, termrangetermenum, termrangetermenum, text

The Lucene TermRangeTermEnum.java source code

package org.apache.lucene.search;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.text.Collator;

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.Term;
import org.apache.lucene.util.StringHelper;

/**
 * Subclass of FilteredTermEnum for enumerating all terms that match the
 * specified range parameters.
 * <p>
 * Term enumerations are always ordered by Term.compareTo().  Each term in
 * the enumeration is greater than all that precede it.
 * @since 2.9
 */
public class TermRangeTermEnum extends FilteredTermEnum {

  private Collator collator = null;
  private boolean endEnum = false;
  private String field;
  private String upperTermText;
  private String lowerTermText;
  private boolean includeLower;
  private boolean includeUpper;

  /**
   * Enumerates all terms greater/equal than <code>lowerTerm
   * but less/equal than <code>upperTerm. 
   * 
   * If an endpoint is null, it is said to be "open". Either or both 
   * endpoints may be open.  Open endpoints may not be exclusive 
   * (you can't select all but the first or last term without 
   * explicitly specifying the term to exclude.)
   * 
   * @param reader
   * @param field
   *          An interned field that holds both lower and upper terms.
   * @param lowerTermText
   *          The term text at the lower end of the range
   * @param upperTermText
   *          The term text at the upper end of the range
   * @param includeLower
   *          If true, the <code>lowerTerm is included in the range.
   * @param includeUpper
   *          If true, the <code>upperTerm is included in the range.
   * @param collator
   *          The collator to use to collate index Terms, to determine their
   *          membership in the range bounded by <code>lowerTerm and
   *          <code>upperTerm.
   * 
   * @throws IOException
   */
  public TermRangeTermEnum(IndexReader reader, String field, String lowerTermText, String upperTermText, 
    boolean includeLower, boolean includeUpper, Collator collator) throws IOException {
    this.collator = collator;
    this.upperTermText = upperTermText;
    this.lowerTermText = lowerTermText;
    this.includeLower = includeLower;
    this.includeUpper = includeUpper;
    this.field = StringHelper.intern(field);
    
    // do a little bit of normalization...
    // open ended range queries should always be inclusive.
    if (this.lowerTermText == null) {
      this.lowerTermText = "";
      this.includeLower = true;
    }
    
    if (this.upperTermText == null) {
      this.includeUpper = true;
    }

    String startTermText = collator == null ? this.lowerTermText : "";
    setEnum(reader.terms(new Term(this.field, startTermText)));
  }

  @Override
  public float difference() {
    return 1.0f;
  }

  @Override
  protected boolean endEnum() {
    return endEnum;
  }

  @Override
  protected boolean termCompare(Term term) {
    if (collator == null) {
      // Use Unicode code point ordering
      boolean checkLower = false;
      if (!includeLower) // make adjustments to set to exclusive
        checkLower = true;
      if (term != null && term.field() == field) { // interned comparison
        if (!checkLower || null==lowerTermText || term.text().compareTo(lowerTermText) > 0) {
          checkLower = false;
          if (upperTermText != null) {
            int compare = upperTermText.compareTo(term.text());
            /*
             * if beyond the upper term, or is exclusive and this is equal to
             * the upper term, break out
             */
            if ((compare < 0) ||
                (!includeUpper && compare==0)) {
              endEnum = true;
              return false;
            }
          }
          return true;
        }
      } else {
        // break
        endEnum = true;
        return false;
      }
      return false;
    } else {
      if (term != null && term.field() == field) { // interned comparison
        if ((lowerTermText == null
            || (includeLower
                ? collator.compare(term.text(), lowerTermText) >= 0
                : collator.compare(term.text(), lowerTermText) > 0))
           && (upperTermText == null
               || (includeUpper
                   ? collator.compare(term.text(), upperTermText) <= 0
                   : collator.compare(term.text(), upperTermText) < 0))) {
          return true;
        }
        return false;
      }
      endEnum = true;
      return false;
    }
  }
}

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