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Re: bug in diskcache?

On 6/3/2010 2:33 PM, Steve Ansari wrote: 
Hi John,

I think I found a bug in the DiskCache comparators:

The problem is a truncation issue when casting from long to int.

In DiskCache.java, line 346, 'FileAgeComparator'
Here is the problem line:
             return (int) (f2.getTime() - f1.getTime());
Here is a fix:
             return  (f2.getTime() - f1.getTime())>  0 ? 1 : -1;

The 'FileSizeComparator' has the same issue but I think is less likely
to show unless really big files are in use.

I hope this helps.

Steve





Here is a short test class using Date instead of File, that shows the
problem:

package steve.test;

import java.text.SimpleDateFormat;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Date;

public class ComparatorTest {

     public static void main(String[] args) {

         try {

             SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
             Date[] dateList = new Date[] {
                 sdf.parse("2002-01-01"),
                 sdf.parse("2002-01-02"),
                 sdf.parse("2002-01-03"),
                 sdf.parse("2002-01-04"),
                 sdf.parse("2002-02-05"),
                 sdf.parse("2002-03-06")
             };

             Arrays.sort(dateList, new DateComparator1());

             System.out.println("sort error: " + Arrays.toString(dateList));

             Arrays.sort(dateList, new DateComparator2());

             System.out.println("sort fix:   "+Arrays.toString(dateList));


         } catch (Exception e) {
             e.printStackTrace();
         }


     }


     // reverse sort - latest come first
     static private class DateComparator1 implements Comparator<Date>  {
         public int compare(Date f1, Date f2) {
             System.out.print(f2+"-"+f1+" =
"+f2.getTime()+"-"+f1.getTime()+" =  int: "+(int) (f2.getTime() -
f1.getTime()));
             System.out.println("  long: "+(f2.getTime() - f1.getTime()));

             return (int) (f2.getTime() - f1.getTime());
         }
     }

     // reverse sort - latest come first
     static private class DateComparator2 implements Comparator<Date>  {
         public int compare(Date f1, Date f2) {
             return  (f2.getTime() - f1.getTime())>  0 ? 1 : -1;
         }
     }

}




woah! thanks a lot, i hadnt seen that problem.

it also needs to return 0 when equal, eg:

// reverse sort - latest come first
static private class FileAgeComparator implements Comparator<File> {
public int compare(File f1, File f2) {
//return (int) (f2.lastModified() - f1.lastModified());
return (f1.lastModified()<f2.lastModified() ? 1 : (f1.lastModified()==f2.lastModified() ? 0 : -1)); // Steve Ansari 6/3/2010
}
}

thanks again!

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