currcomparator.java

J2ME程序设计实例教程的源码

import java.io.IOException;
import javax.microedition.rms.RecordComparator;

/**
 * 该类实现了课程的排序功能
 */
class CurrComparator implements RecordComparator {
    private Curriculum curr1;
    private Curriculum curr2;
    
    public CurrComparator() {
        curr1 = new Curriculum(null);
        curr2 = new Curriculum(null);
    }
    
    //接口RecordComparator中的方法，在获取记录枚举时，该方法不断被回调。
    //data1, data2为记录存储中的两条记录，方法按一定的规则比较两条记录的大小。
    public int compare(byte[] data1, byte[] data2) {
        try {                                             
            curr1.setData(data1);
            curr2.setData(data2);
        }                                                 
        catch(IOException ioe) {
            System.out.println("错误：" + ioe.toString());
            return RecordComparator.EQUIVALENT;
        }                                
        int bjWeek = curr1.getDay() - curr2.getDay(); 
        int bjJie = curr1.getTime() - curr2.getTime();  
        if(bjWeek > 0) {                              
            return RecordComparator.FOLLOWS;           
        }   
        else if(bjWeek < 0) {                         
            return RecordComparator.PRECEDES;          
        }                                             
        else {                                        
            if(bjJie > 0) {                           
                return RecordComparator.FOLLOWS;       
            }                                         
            else if(bjJie < 0) {                      
                return RecordComparator.PRECEDES;      
            }                                         
        }
        
        return RecordComparator.EQUIVALENT;
    }
}