I have several files, thing is that i need to know which one was the last created according to the numbers I give them automatically.
For example if i have: file1, file2, file3 I want to receive the file3. I can't do this with "last modified" because I have other folders and files in the same directory.
Also to this last file I would like to increment his number in 1.
Put the files in a list and sort it lexically, then take the last one.
Ofcourse you have to filter out the ones you are looking for with regex or contains/startswith/endswith
Here is an alternate simple solution.
import java.io.File;
public class FileUtility {
private static final String FOLDER_PAHT = "D:\\Test";
private static final String FILE_PREFIX = "file";
/**
* @param args
*/
public static void main(String[] args) {
int lastFileNumber = getLastFileNumber();
System.out.println("In folder " + FOLDER_PAHT + " last file is " + FILE_PREFIX + lastFileNumber);
if(incrementFileNumber(lastFileNumber)) {
System.out.println("After incrementing the last file becomes : FILE_PREFIX" + lastFileNumber + 1);
} else {
System.out.println("Some error occured while updating file number.");
}
}
private static int getLastFileNumber(){
int maxFileNumber = 0;
File folder = new File(FOLDER_PAHT);
File[] listOfFiles = folder.listFiles();
for (int i = 0; i < listOfFiles.length; i++) {
String fileName = listOfFiles[i].getName();
if (listOfFiles[i].isFile() && fileName.contains(FILE_PREFIX)) {
try {
int fileNumber = Integer.parseInt(fileName.substring(FILE_PREFIX.length(), fileName.indexOf(".")));
if(maxFileNumber < fileNumber) {
maxFileNumber = fileNumber;
}
} catch (NumberFormatException e) {
// Because there can be files with starting name as FILE_PREFIX but not valid integer appended to them.
//NOthing to do
}
}
}
return maxFileNumber;
}
private static boolean incrementFileNumber(final int oldNumber) {
File oldfile =new File(FOLDER_PAHT + File.separator + FILE_PREFIX + oldNumber);
File newfile =new File(FOLDER_PAHT + File.separator + FILE_PREFIX + (oldNumber + 1) + ".txt");
return oldfile.renameTo(newfile);
}
}
Ok, here's an alternative. I'm assuming that the file name is known and they have the same name.
public static void main(String[] args) {
File dir = new File("directory of the files");
File [] files = dir.listFiles(new FilenameFilter() {
@Override
public boolean accept(File dir, String name) {
return name.startsWith("folder");
}
});
for (File file : files) {
System.out.println(file.getName());
}
System.out.println("---------");
List<File> myFile = new ArrayList<>(Arrays.asList(files));
Collections.sort(myFile, new Comparator<File>() {
@Override
public int compare(File f1, File f2) {
// TODO Auto-generated method stub
int numberF1 = Integer.parseInt(f1.getName().replace("folder",""));
int numberF2 = Integer.parseInt(f2.getName().replace("folder",""));
return Integer.compare(numberF1, numberF2);
}
});
for (File file : myFile) {
System.out.println(file.getName());
}
}
Output :
folder10
folder2
folder20
folder250
---------
folder2
folder10
folder20
folder250
public static void main (String[] args) throws Exception
{
File foldersContainer = new File("c:/test");
String latestFileName = "";
Integer highestFileNumber = 0;
for (File tmpFile : foldersContainer.listFiles()){
if (tmpFile.isFolder()) {
int currentNumber = extractFileNumber(tmpFile.getName());
if (currentNumber > highestFileNumber){
highestFileNumber = currentNumber;
latestFileName = tmpFile.getName();
}
}
}
latestFileName.replace(highestFileNumber.toString(),
(++highestFileNumber).toString());
System.out.println("Latest file (incremented): " + latestFileName);
}
private static int extractFileNumber(String name){
for (int x=name.length()-1; x >= 0; x--)
if (!Character.isDigit(name.charAt(x)))
return Integer.parseInt(name.substring(x+1));
return -1;
}
If the filename before the last number can contain numbers, then you should use lastIndexOf to be sure of finding only the occurrence you really want to increment.
instead of
latestFileName.replace(highestFileNumber.toString(),
(++highestFileNumber).toString());
you should use
latestFileName = latestFileName
.substring(0,latestFileName.lastIndexOf(highestFileNumber.toString()))
.concat((++highestFileNumber).toString());
