Re: Math.random()

From:

maya <maya778899@yahoo.com>

Newsgroups:

comp.lang.java.help

Date:

Mon, 10 Mar 2008 12:45:31 -0400

Message-ID:

<47d565b4$1@news.x-privat.org>

Lew wrote:

maya wrote:

so I now have:

ArrayList photos = new ArrayList();

If you used generics you'd see that this is a List <File>, not a List
<String>.

    for (int i=0; i < textFileNames.length; i++) {
        photos.add(new File(textFileNames[i]));
    }
           Collections.shuffle(photos, new Random());

You don't really need a new Random().

String[] photosArr = new String[photos.size()];
photos.toArray(photosArr); // runtime error on this line..

Because you're trying to jam a bunch of Files into an array of String.

it compiles fine,

Because you don't use generics. With generics you'd have had an error
and you'd know why it didn't work.

but get a runtime error, thus:
Exception in thread "main" java.lang.ArrayStoreException
line 40 is: photos.toArray(photosArr);

And now you know.

thank you very much to all for your help.. I finally managed, thus:

public class renameRandom {

public static void main(String[] args) {

    int posDot;
    String _temp = "";
    String no = "";
    File oldFile;
    int __indx;
    int _indx;
    int indx;

    File directory = new File(System.getProperty("user.dir"));

    // if no arg passed start naming of imgs @ "1"
    // else start at whatever no. is passed...
    if (null == args || args.length < 1) {
      no = "1";
    } else {
      no = args[0];
    }
    __indx = Integer.parseInt(no);
     _indx = __indx - 1;

    String[] textFileNames = directory.list(new FilenameFilter() {
      public boolean accept(File dir, String name) {
          return name.endsWith(".jpg") || name.endsWith( ".JPG");
         }
    });

    ArrayList photos = new ArrayList();

    for (int i=0; i < textFileNames.length; i++) {
      System.out.println(textFileNames[i] + " -- " + i);
      photos.add(new File(textFileNames[i]));
    }

    System.out.println("");

    Collections.shuffle(photos);
    Object _photosArr[] = photos.toArray();
    String photosArr = "";
    File newFile;

    for (int i = 1; i < _photosArr.length+1; ++i) {
      photosArr = _photosArr[i-1].toString();
      posDot = photosArr.indexOf(".");
      _temp = photosArr.substring(0,posDot);
      oldFile = new File(_temp + ".jpg");
      indx = i + _indx;
      newFile = new File(indx + ".jpg");
      oldFile.renameTo(newFile);
      System.out.println(_photosArr[i-1] + " -- " + newFile);
      System.out.println(photosArr + " ** " + newFile + "\n");
             // above line u see it prints out correct new names....
    }

     }
}

however, a problem remains:

1) if, after renaming, I have, say, imgs 1.jpg thru 15.jpg, then remove,
for ex, 8.jpg and 9.jpg, and run class again, it still skips these two
numbers and last img is still 15.jpg.. (but if you run the class and
look @ printouts in console it shows correct names for newFile var...

in general I find class does not work well if when run the class files
have already been renamed once to 1.jpg, etc.. as opposed to if files
still have orig names (DSC_0004.jpg, etc..)

once again thank you all very much... this is the hardest thing I have
tried to do in java...