2012-03-15 61 views
3

相同的代码在两个J2ME & NetBeans的下面的代码运行:获得不同的输出,同时运行在J2ME&的NetBeans

该代码可用于记录滤波(查询的记录)。

问题是,我们在j2me中运行此代码时,它从头开始执行搜索,而在NetBeans中则是从反向搜索。

 import javax.microedition.rms.*; 
     import javax.microedition.midlet.*; 
     import javax.microedition.lcdui.*; 
     import java.io.*; 
     import javax.microedition.rms.RecordFilter; 
     public class SearchExample extends MIDlet implements CommandListener 
     { 
     private Display display; 
     private Alert alert; 
     private Form form; 
     private Command exit; 
     private Command start; 
     private RecordStore recordstore = null; 
     private RecordEnumeration recordEnumeration = null; 
     private Filter filter = null; 
     public SearchExample() 
     { 
     display = Display.getDisplay(this); 
     exit = new Command("Exit", Command.SCREEN, 1); 
     start = new Command("Start", Command.SCREEN, 1); 
     form = new Form("Mixed RecordEnumeration", null); 
     form.addCommand(exit); 
     form.addCommand(start); 
     form.setCommandListener(this); 
     } 
     public void startApp() 
     { 
     display.setCurrent(form); 
     } 
     public void pauseApp() 
     { 
     } 
     public void destroyApp(boolean unconditional) 
     { 
     } 
     public void commandAction(Command command, Displayable displayable) 
     { 
     if (command == exit) 
     { 
     destroyApp(true); 
     notifyDestroyed(); 
     } 
     else if (command == start) 
     { 
     try 
     { 
     recordstore = RecordStore.openRecordStore("myRecordStore", true); 
     } 
     catch (Exception error) 
     { 
     alert = new Alert("Error Creating",error.toString(), null, AlertType.WARNING); 
     alert.setTimeout(Alert.FOREVER); 
     display.setCurrent(alert); 
     } 
     try 
     { 
     String outputData[] = {"Mary", "Adam","dancebob","bobby","bob1"}; 
     for (int x = 0 ; x < outputData.length; x++) 
     { 

     byte[] byteOutputData = outputData[x].getBytes(); 
     recordstore.addRecord(byteOutputData, 0,byteOutputData.length); 
     } 
     } 
     catch (Exception error) 
     { 
     alert = new Alert("Error Writing",error.toString(), null, AlertType.WARNING); 
     alert.setTimeout(Alert.FOREVER); 
     display.setCurrent(alert); 
     } 
     try 
     { 
     filter = new Filter("Bob"); 
     StringBuffer sbuf=new StringBuffer(); 
     recordEnumeration = recordstore.enumerateRecords(filter, null, false); 
     if (recordEnumeration.numRecords() > 0) 
     { 
     for(int i=0;i<recordEnumeration.numRecords();i++){ 
     String string = new String(recordEnumeration.nextRecord()); 
     sbuf.append(string+"\n"); 
     } 

     alert = new Alert("Reading", sbuf.toString(),null, AlertType.WARNING); 
     alert.setTimeout(Alert.FOREVER); 
     display.setCurrent(alert); 
     } 
     } 
     catch (Exception error) 
     { 
     alert = new Alert("Error Reading",error.toString(), null, AlertType.WARNING); 
     alert.setTimeout(Alert.FOREVER); 
     display.setCurrent(alert); 
     } 
     try 
     { 
     recordstore.closeRecordStore(); 
     } 
     catch (Exception error) 
     { 
     alert = new Alert("Error Closing",error.toString(), null, AlertType.WARNING); 
     alert.setTimeout(Alert.FOREVER); 
     display.setCurrent(alert); 
     } 
     if (RecordStore.listRecordStores() != null) 
     { 
     try 
     { 
     RecordStore.deleteRecordStore("myRecordStore"); 
     recordEnumeration.destroy(); 
     filter.filterClose(); 
     } 
     catch (Exception error) 
     { 
     alert = new Alert("Error Removing",error.toString(), null, AlertType.WARNING); 
     alert.setTimeout(Alert.FOREVER); 
     display.setCurrent(alert); 
     } 
     } 

     } 
     } 
     } 
     class Filter implements RecordFilter 
     { 
     private String search = null; 
     private ByteArrayInputStream inputstream = null; 
     private DataInputStream datainputstream = null; 
     public Filter(String search) 
     { 
     this.search = search.toLowerCase(); 
     } 
     public boolean matches(byte[] suspect) 
     { 
     String string = new String(suspect).toLowerCase(); 

     if (string!= null && string.indexOf(search) != -1) 
      return true; 
     else 
      return false; 
     } 

     public void filterClose() 
     { 
     try 
     { 
     if (inputstream != null) 
     { 
     inputstream.close(); 
     } 
     if (datainputstream != null) 
     { 
     datainputstream.close(); 
     } 
     } 
     catch (Exception error) 
     { 
     } 
     } 
     } 

回答

4

你的代码片断是相当大的和格式是坏的,所以有可能是我没有注意到其他一些错误,但如果你担心的是遍历枚举你在这行创建的顺序:

recordEnumeration = recordstore.enumerateRecords(filter, null, false); 

那么这是正常的行为。 MIDP RMS API documentation指出,当第二个参数是null(并且在您的代码中它是),则记录按未定义的顺序遍历。

请参阅下面的报价,并注意您可能会认为这关系到RecordComparator comparator

public RecordEnumeration enumerateRecords(RecordFilter filter, 
             RecordComparator comparator, 
             boolean keepUpdated) 
           throws RecordStoreNotOpenException 

Returns an enumeration for traversing a set of records in the record store 
    in an optionally specified order. 

The filter, if non-null, will be used to determine what subset 
    of the record store records will be used. 

The comparator, if non-null, will be used to determine the order 
    in which the records are returned. 

If both the filter and comparator is null, the enumeration will traverse 
    all records in the record store in an undefined order. This is the most 
    efficient way to traverse all of the records in a record store. If a filter 
    is used with a null comparator, the enumeration will traverse the filtered 
    records in an undefined order. The first call to RecordEnumeration.nextRecord() 
    returns the record data from the first record in the sequence. Subsequent calls 
    to RecordEnumeration.nextRecord() return the next consecutive record's data. 
    To return the record data from the previous consecutive from any given point 
    in the enumeration, call previousRecord(). On the other hand, if after creation 
    the first call is to previousRecord(), the record data of the last element 
    of the enumeration will be returned. Each subsequent call to previousRecord() 
    will step backwards through the sequence. 

Parameters: 
    filter - if non-null, will be used to determine what subset of the 
    record store records will be used 
    comparator - if non-null, will be used to determine the order in which 
    the records are returned 
    ... 

细节,因为它仅仅是一个幸运的巧合,Netbeans的模拟器每次运行MIDlet的时间遍历同样的方式记录;理论上允许在每次运行中改变顺序。