QryIopTerm.java

/**
 *  Copyright (c) 2016, Carnegie Mellon University.  All Rights Reserved.
 */
import java.io.*;
import java.util.*;

/**
 *  The TERM operator for all retrieval models.  The TERM operator stores
 *  information about a query term, for example "apple" in the query
 *  "#AND (apple pie).  Although it may seem odd to use a query
 *  operator to store a term, doing so makes it easy to build
 *  structured queries with nested query operators.
 *
 */
public class QryIopTerm extends QryIop {

  private String term;

  /**
   *  The term is assumed to match the body field.
   *  @param termString A term string.
   */
  public QryIopTerm(String termString) {
    this.term = termString;
    this.field = "body";	// Default field if none is specified.
  }

  /**
   *  The term matches in the specified field.
   *  @param termString A term string.
   *  @param fieldString A field string.
   */
  public QryIopTerm(String termString, String fieldString) {
    this.term = termString;
    this.field = fieldString;
  }

  /**
   *  Evaluate the query operator; the result is an internal inverted
   *  list that may be accessed via the internal iterators.
   *  @throws IOException Error accessing the Lucene index.
   */
  protected void evaluate () throws IOException {
    this.invertedList = new InvList(this.term, this.field);
  }

  /**
   *  Get a string version of this query operator.  
   *  @return The string version of this query operator.
   */
  public String toString(){
    return (this.term + "." + this.field);
  }
}