alertdatabase.java

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/*
 * @(#)AlertDatabase.java	1.2 03/01/22
 *
 * Copyright (c) 1999-2003 Sun Microsystems, Inc. All rights reserved. 
 * PROPRIETARY/CONFIDENTIAL
 * Use is subject to license terms
 */

package example.stock;

import javax.microedition.rms.*;
import java.util.*;

/**
 * <p>This class provides an implementation of the <code>Database</code>
 * class specific to alert records.</p>
 */
public class AlertDatabase extends Database {

    /**
     * Default Constructor
     */
    public AlertDatabase() {
        rc = new AlertComparator();
    }

    /**
     * <p>This methods cleans out the database of all alerts that match the
     * <code>tkrSymbol</code> passed in.  An appropriate use would be when
     * removing a stock from the database, all alerts for that stock are no
     * longer valid, so call this method then.</p>
     *
     * @param tkrSymbol The name of the stock to match with alerts
     */
    public synchronized void removeUselessAlerts(String tkrSymbol) {
        Enumeration IDs = recordIDs.elements();
        while (IDs.hasMoreElements()) {            
            int index = ((Integer) IDs.nextElement()).intValue();
            try {
                String data = new String(database.getRecord(index));
                data = data.substring(0, data.indexOf(';'));
                if (data.equals(tkrSymbol)) {
                    database.deleteRecord(index);
                    recordIDs.removeElement(new Integer(index));
                }
            } catch (RecordStoreException rse) {
                return;
            }
        }
    }

    /**
     * <p>Get a <code>RecordEnumeration</code> of records in the database who
     * match the <code>AlertFilter</code> conditions</p>
     *
     * @return <code>RecordEnumeration</code> of all stock records that match
     *         the <code>RecordFilter</code>
     * @param tkrSymbol The name of the stock to retrieve alerts for
     * @param price The price of the stock to retrieve alerts for
     * @throws <code>RecordStoreNotOpenException</code> is thrown when
     *         trying to close a <code>RecordStore</code> that is not open
     */
    public synchronized RecordEnumeration enumerateRecords(String tkrSymbol,
							   int price)
            throws RecordStoreNotOpenException {
        return database.enumerateRecords(new AlertFilter(tkrSymbol, price),
					 null, false);
    }

    /**
     * <p>Filters the records based on stock symbol and price.  If price is
     * passed as 0 then all records (excluding the first one that stores the
     * lastID) are selected</p>
     *
     * @see javax.microedition.rms.RecordFilter
     */
    private class AlertFilter implements RecordFilter {

        /**
         * <p>The stock symbol to filter with</p>
         */
        private String symbol = null;

        /**
         * <p>The price to filter with</p>
         */
        private int    price  = 0;

        /**
         * <p>Constructor for the <code>AlertFilter</code></p>
         *
         * @param tkrSymbol The name of the stock to filter for
         * @param matchPrice The price to match with the alert
         */
        public AlertFilter(String tkrSymbol, int matchPrice) {
            symbol = tkrSymbol;
            price = matchPrice;
        }

        /**
         * <p>Returns true if the candidate matches the symbol and price<p>
         *
         * @returns true if the candidate matches the criteria
         * @param candidate The data to check against the criteria
         */
        public boolean matches(byte[] candidate) {
            if (candidate.length > 4) {
                if (price == 0) {
		    return true; 
		}
                String c = new String(candidate);
                if (symbol.equals(c.substring(0, c.indexOf(';')))) {
                    if (price >= 
			Integer.valueOf(c.substring(c.indexOf(';')+1, 
						    c.length()))
					.intValue()) {
                        return true;
                    }
                }
            }
            return false;
        }
    }

    /**
     *  <p>Class to compare two records and see if they are equal</p>
     *
     * @see javax.microedition.rms.RecordComparator
     */
    private class AlertComparator implements RecordComparator {
        /**
         * <p>Checks to see if rec1 matches rec2</p>
         *
         * @returns <code>RecordComparator.EQUIVALENT</code> if the records
         *          match or <code>Integer.MAX_VALUE</code> if they don't
         * @param rec1 the data to compare against
         * @param rec2 the data to compare with
         */
        public int compare(byte[] rec1, byte[] rec2) {
            System.out.println(new String(rec1) + " ?==? " + new String(rec2));
            String record1 = new String(rec1);
            String record2 = new String(rec2);
            if (record1.equals(record2)) {
                return RecordComparator.EQUIVALENT;
            }
            return Integer.MAX_VALUE;
        }
    }
}