www.pudn.com > j2mewireless_examples.zip > SimpleComparator.java

/*
 * Copyright (c) 2000-2001 Sun Microsystems, Inc. All Rights Reserved.
 */

package examples.addressbook;
import java.lang.*;
import java.io.*;
import java.util.*;
import javax.microedition.rms.*;

/**
 * This class implements the RecordComparator interface.
 * It works on the records created by SimpleRecord.
 * It sorts on either first name or last name.
 */
class SimpleComparator implements RecordComparator {

    /**
     * Sorting values (sort by first or last name)
     */
    public final static int SORT_BY_FIRST_NAME = 1;
    public final static int SORT_BY_LAST_NAME = 2;

    /**
     * Sort order.  Set by constructor.
     */
    private int sortOrder = -1;

    /**
     * Public constructor: sets the sort order to be
     * used for this instantiation.
     *
     * Sanitize s: if it is not one of the
     * valid sort codes, set it to SORT_BY_LAST_NAME
     * silently.
     *  s  the desired sort order
     */
    SimpleComparator(int s) {
        switch (s) {
        case SORT_BY_FIRST_NAME:
        case SORT_BY_LAST_NAME:
            this.sortOrder = s;
            break;
        default:
            this.sortOrder = SORT_BY_LAST_NAME;
            break;
        }
    }

    /**
     * This is the compare method. It takes two
     * records, and depending on the sort order
     * extracts and lexicographically compares the
     * subfields as two Strings.
     *
     *  r1  First record to compare
     *  r2  Second record to compare
     * return one of the following:
     * 
     * RecordComparator.PRECEDES
     *     if r1 is lexicographically less than r2
     * RecordComparator.FOLLOWS
     *     if r1 is lexicographically greater than r2
     * RecordComparator.EQUIVALENT
     *     if r1 and r2 are lexicographically equivalent
     */
    public int compare(byte[] r1,
                       byte[] r2) {

        String n1 = null;
        String n2 = null;

        // Based on sortOrder, extract the correct fields
        // from the record and convert them to lower case
        // so that we can perform a case-insensitive compare.
        if (sortOrder == SORT_BY_FIRST_NAME) {
            n1 = SimpleRecord.getFirstName(r1).toLowerCase();
            n2 = SimpleRecord.getFirstName(r2).toLowerCase();
        } else if (sortOrder == SORT_BY_LAST_NAME) {
            n1 = SimpleRecord.getLastName(r1).toLowerCase();
            n2 = SimpleRecord.getLastName(r2).toLowerCase();
        }

        int n = n1.compareTo(n2);
        if (n < 0) {
            return RecordComparator.PRECEDES;
        }
        if (n > 0) {
            return RecordComparator.FOLLOWS;
        }

        return RecordComparator.EQUIVALENT;
    }
}