I need to frame a file name as name_<date>_N
, where N is a counter for the number of similar files.
String fileName = "name";
String fileNameWithDate = fileName + "_"+ new SimpleDateFormat("MMM_dd_yyyy").format(cal.getTime());
If I try to download more times for a given date, the count should be incremented by 1; for example, name_Dec_10_2015_N
. How do I get filename with date and incremented by 1?
As @MadProgrammer already wrote you need to do it in following steps
- get a list of all files matching your pattern
- find the file with the highest counter
- created the file name for the increased counter
Here is short snippet which you can use as a starting point (the handling of edge cases, like: no file found, etc., are intentionally omited and part of your own work)
public class IncreaseCounter {
static final SimpleDateFormat FILE_DATE = new SimpleDateFormat("MMM_dd_yyyy");
public static void main(String[] args) {
// filter files which matches the given pattern
FilenameFilter fileNameFilter = new FilenameFilter() {
@Override
public boolean accept(File dir, String name) {
return name.matches("^name_..._.._.....*\\.txt");
}
};
// needed to sort the file list based on the file counter
Comparator<File> sortByCounter = new Comparator<File>() {
@Override
public int compare(File file1, File file2) {
return getFileCounter(file1.getName()) - getFileCounter(file2.getName());
}
};
String filesLocation = "resources/";
int highestCounter = 0;
// read the files matching the filter
File[] listFiles = new File(filesLocation).listFiles(fileNameFilter);
List<File> files = Arrays.asList(listFiles);
// sort the files by their file counter
Collections.sort(files, sortByCounter);
// get the highest counter
String fileWithHighestCounter = files.get(files.size() - 1).getName();
highestCounter = getFileCounter(fileWithHighestCounter);
String nextFileName = String.format("name_%s_%d.txt",
FILE_DATE.format(new Date()),
highestCounter + 1
);
System.out.println("nextFileName = " + nextFileName);
}
/**
* Extract the file counter.
* @param fileName the file name
* @return 0 - if the file has no counter, otherwise the counter value
*/
static int getFileCounter(String fileName) {
String namePatternWithCounter = "^name_..._.._...._*(.*)\\.txt";
String counterString = fileName.replaceAll(namePatternWithCounter, "$1");
if (counterString.isEmpty()) {
return 0;
}
return Integer.parseInt(counterString);
}
}