recordcomparator.java

有关j2me的很好的例子可以研究一下

/*
 * @(#)RecordComparator.java	1.8 01/06/19
 * Copyright (c) 2000-2001 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Copyright 2000 Motorola, Inc. All Rights Reserved.
 * This notice does not imply publication.
 */

package javax.microedition.rms; 

/** 
 * An interface defining a comparator which compares two records (in an 
 * implementation-defined manner) to see if they match or what their 
 * relative sort order is. The application implements this interface 
 * to compare two candidate records. The return value must indicate 
 * the ordering of the two records. The compare method is called by 
 * RecordEnumeration to sort and return records in an application 
 * specified order. For example: 
 *
 * // return the first byte after thedb headers
 * RecordComparator c = new AddressRecordComparator(); 
 * if (c.compare(recordStore.getRecord(rec1), recordStore.getRecord(rec2)) 
 * == RecordComparator.PRECEDES) return rec1; 
 * 
 * @version MIDP 1.0
 * @author Jim Van Peursem 
 */
public interface RecordComparator 
{ 
    /** 
     * EQUIVALENT means that in terms of search or sort order, the 
     * two records are the same. This does not necessarily mean that 
     * the two records are identical. 
     * <P>The value of EQUIVALENT is 0.</P> 
     */
    public static final int EQUIVALENT = 0;
    
    /** 
     * FOLLOWS means that the left (first parameter) record <em>follows</em> 
     * the right (second parameter) record in terms of search or 
     * sort order. 
     * <P>The value of FOLLOWS is 1.</P> 
     */
    public static final int FOLLOWS = 1;
    
    /** 
     * PRECEDES means that the left (first parameter) record <em>precedes</em> 
     * the right (second parameter) record in terms of search or 
     * sort order. 
     * <P>The value of PRECEDES is -1.</P> 
     */
    public static final int PRECEDES = -1;
    
    /** 
     * Returns <code>RecordComparator.PRECEDES</code> if rec1 
     * precedes rec2 in sort order, or <code>RecordComparator.FOLLOWS</code> 
     * if rec1 follows rec2 in sort order, or 
     * <code>RecordComparator.EQUIVALENT</code> if rec1 and rec2 
     * are equivalent in terms of sort order. 
     * 
     * @param rec1 The first record to use for comparison. Within this 
     * method, the application must treat this parameter as read-only. 
     * @param rec2 The second record to use for comparison. Within this 
     * method, the application must treat this parameter as read-only. 
     * @return <code>RecordComparator.PRECEDES</code> if rec1 precedes 
     * rec2 in sort order, or <code>RecordComparator.FOLLOWS</code> if 
     * rec1 follows rec2 in sort order, or 
     * <code>RecordComparator.EQUIVALENT</code> if rec1 and rec2 
     * are equivalent in terms of sort order. 
     */
    public abstract int compare(byte[] rec1, byte[] rec2); 
}