J2ME:rms的排序

最新推荐文章于 2019-06-01 19:06:05 发布

原创最新推荐文章于 2019-06-01 19:06:05 发布 · 592 阅读

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本文介绍了一个使用Java ME实现的记录存储应用案例。该案例通过创建一个实现了RecordComparator接口的类compareRecord，演示了如何对存储在RecordStore中的记录进行排序和比较。文中详细展示了如何打开记录存储、添加记录以及通过实现RecordComparator接口的方法来定义记录间的比较规则。

import javax.microedition.midlet.MIDlet;
import javax.microedition.midlet.MIDletStateChangeException;
import javax.microedition.rms.RecordComparator;
import javax.microedition.rms.RecordEnumeration;
import javax.microedition.rms.RecordStore;
import javax.microedition.rms.RecordStoreException;
import javax.microedition.rms.RecordStoreFullException;
import javax.microedition.rms.RecordStoreNotFoundException;

public class compareRecord extends MIDlet implements RecordComparator{
RecordStore rs=null;
public compareRecord() {
// TODO Auto-generated constructor stub
}

protected void destroyApp(boolean arg0) throws MIDletStateChangeException {
// TODO Auto-generated method stub

}

protected void pauseApp() {
// TODO Auto-generated method stub

}

protected void startApp() throws MIDletStateChangeException {
  // TODO Auto-generated method stub
  try {
   rs=RecordStore.openRecordStore("rs", true);
   rs.addRecord("443".getBytes(), 0, "443".getBytes().length);
   rs.addRecord("34".getBytes(), 0, "34".getBytes().length);
   rs.addRecord("344".getBytes(), 0, "344".getBytes().length);
   rs.addRecord("23".getBytes(), 0, "23".getBytes().length);
   rs.addRecord("354".getBytes(), 0, "354".getBytes().length);


   //方法一，枚举遍历
   RecordEnumeration re= rs.enumerateRecords(null, this, false); //能发现失效的ID并自动跳过
   while(re.hasNextElement())
   {
    System.out.println(new String(re.nextRecord()));
   }
   rs.closeRecordStore();
  } catch (RecordStoreFullException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (RecordStoreNotFoundException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (RecordStoreException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
}

public int compare(byte[] arg0, byte[] arg1) {
  // TODO Auto-generated method stub
  int num1=Integer.parseInt(new String(arg0));
  int num2=Integer.parseInt(new String(arg1));
  if(num1<num2)
   return RecordComparator.FOLLOWS;     //arg0放到arg1的后面
  else if(num2<num1)
            return RecordComparator.PRECEDES;    //arg0放到arg1的前面
  return RecordComparator.EQUIVALENT;      //arg0和arg1无分先后
}

}