Develop Reference

How to increment the filename number if the file exists

How can I increment the filename if the file already exists?
Here's the code that I am using -
int num = 0;
String save = at.getText().toString() + ".jpg";
File file = new File(myDir, save);
if (file.exists()) {
save = at.getText().toString() + num + ".jpg";
file = new File(myDir, save);
num++;
}
This code works, but only two files are saved, like file.jpg and file2.jpg.

This problem is to always initialize num = 0, so if file exists, it saves file0.jpg and does not check whether file0.jpg exists.
So, to code work. You should check until it is available:
int num = 0;
String save = at.getText().toString() + ".jpg";
File file = new File(myDir, save);
while(file.exists()) {
save = at.getText().toString() + (num++) + ".jpg";
file = new File(myDir, save);
}

Try this:
File file = new File(myDir, at.getText().toString() + ".jpg");
for (int num = 0; file.exists(); num++) {
file = new File(myDir, at.getText().toString() + num + ".jpg");
}
// Now save/use your file here

In addition to the first answer, I made some more changes:
private File getUniqueFileName(String folderName, String searchedFilename) {
int num = 1;
String extension = getExtension(searchedFilename);
String filename = searchedFilename.substring(0, searchedFilename.lastIndexOf("."));
File file = new File(folderName, searchedFilename);
while (file.exists()) {
searchedFilename = filename + "(" + (num++) + ")" + extension;
file = new File(folderName, searchedFilename);
}
return file;
}

int i = 0;
String save = at.getText().toString();
String filename = save +".jpg";
File f = new File(filename);
while (f.exists()) {
i++;
filename =save+ Integer.toString(i)+".jpg";
f = new File(filename);
}
f.createNewFile();

You can avoid the code repetition of some of the answers here by using a do while loop
Here's an example using the newer NIO Path API introduced in Java 7
Path candidate = null;
int counter = 0;
do {
candidate = Paths.get(String.format("%s-%d",
path.toString(), ++counter));
} while (Files.exists(candidate));
Files.createFile(candidate);

Kotlin version:
private fun checkAndRenameIfExists(name: String): File {
var filename = name
val extension = "pdf"
val root = Environment.getExternalStorageDirectory().absolutePath
var file = File(root, "$filename.$extension")
var n = 0
while (file.exists()) {
n += 1
filename = "$name($n)"
file = File(root, appDirectoryName + File.separator + "$filename.$extension")
}
return file
}

Another simple logic solution to get the unique file name under a directory using Apache Commons IO using WildcardFileFilter to match the file name and get the number of exists with the given name and increment the counter.
public static String getUniqueFileName(String directory, String fileName) {
String fName = fileName.substring(0, fileName.lastIndexOf("."));
Collection<File> listFiles = FileUtils.listFiles(new File(directory), new WildcardFileFilter(fName + "*", IOCase.INSENSITIVE), DirectoryFileFilter.DIRECTORY);
if(listFiles.isEmpty()) {
return fName;
}
return fName.concat(" (" + listFiles.size() + ")");
}

This is the solution I use to handle this case. It works for folders as well as for files.
var destination = File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS), "MyFolder")
if (!destination.exists()) {
destination.mkdirs()
} else {
val numberOfFileAlreadyExist =
destination.listFiles().filter { it.name.startsWith("MyFolder") }.size
destination = File(
Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS),
"MyFolder(${numberOfFileAlreadyExist + 1})"
)
destination.mkdirs()
}

Having needed to solve this problem in my own code, I took Tejas Trivedi's answer, made it work like Windows when you happen to download the same file several times.
// This function will iteratively to find a unique file name to use when given a file: example (###).txt
// More or less how Windows will save a new file when one already exists: 'example.txt' becomes 'example (1).txt'.
// if example.txt already exists
private File getUniqueFileName(File file) {
File originalFile = file;
try {
while (file.exists()) {
String newFileName = file.getName();
String baseName = newFileName.substring(0, newFileName.lastIndexOf("."));
String extension = getExtension(newFileName);
Pattern pattern = Pattern.compile("( \\(\\d+\\))\\."); // Find ' (###).' in the file name, if it exists
Matcher matcher = pattern.matcher(newFileName);
String strDigits = "";
if (matcher.find()) {
baseName = baseName.substring(0, matcher.start(0)); // Remove the (###)
strDigits = matcher.group(0); // Grab the ### we'll want to increment
strDigits = strDigits.substring(strDigits.indexOf("(") + 1, strDigits.lastIndexOf(")")); // Strip off the ' (' and ').' from the match
// Increment the found digit and convert it back to a string
int count = Integer.parseInt(strDigits);
strDigits = Integer.toString(count + 1);
} else {
strDigits = "1"; // If there is no (###) match then start with 1
}
file = new File(file.getParent() + "/" + baseName + " (" + strDigits + ")" + extension); // Put the pieces back together
}
return file;
} catch (Error e) {
return originalFile; // Just overwrite the original file at this point...
}
}
private String getExtension(String name) {
return name.substring(name.lastIndexOf("."));
}
Calling getUniqueFileName(new File('/dir/example.txt') when 'example.txt' already exists while generate a new File targeting '/dir/example (1).txt' if that too exists it'll just keep incrementing number between the parentheses until a unique file is found, if an error happens, it'll just give the original file name.
I hope this helps some one needing to generate a unique file in Java on Android or another platform.

This function returns the exact new file with an increment number for all kind of extensions.
private File getFileName(File file) {
if (file.exists()) {
String newFileName = file.getName();
String simpleName = file.getName().substring(0, newFileName.indexOf("."));
String strDigit = "";
try {
simpleName = (Integer.parseInt(simpleName) + 1 + "");
File newFile = new File(file.getParent() + "/" + simpleName + getExtension(file.getName()));
return getFileName(newFile);
}
catch (Exception e){
}
for (int i=simpleName.length()-1; i>=0; i--) {
if (!Character.isDigit(simpleName.charAt(i))) {
strDigit = simpleName.substring(i + 1);
simpleName = simpleName.substring(0, i+1);
break;
}
}
if (strDigit.length() > 0) {
simpleName = simpleName + (Integer.parseInt(strDigit) + 1);
}
else {
simpleName += "1";
}
File newFile = new File(file.getParent() + "/" + simpleName + getExtension(file.getName()));
return getFileName(newFile);
}
return file;
}
private String getExtension(String name) {
return name.substring(name.lastIndexOf("."));
}

Java - renaming output file if name already exists with an increment, taking into account existing increments

building an Android app i came across the need to do some file copying. I would like a way to get new filenames in the event of a filename allready being used by adding a "(increment)" string in the filename. for example
text.txt ---> text(1).txt
The algorith should account for the following
1) if text.txt exists the new file name should NEVER be text.txt(1)
2) if text(1).txt exists then new filename should be text(2).txt not text(1)(1).txt
3) if text(1)foo.txt exists the new filename should be text(1)foo(1).txt
I've allready done the first but I'm having difficulties with the second. Regular expressions is not my strong suit!(It's not mandatory to use Regex. every approach is welcome) Some help ?
ANSWER:
combining my original code and one of the answers here I ended up with this which works very well for me in all cases regardless of file having an extension or not:
public static File getFinalNewDestinationFile(File destinationFolder, File fileToCopy){
String destFolderPath = destinationFolder.getAbsolutePath()+File.separator;
File newFile = new File(destFolderPath + fileToCopy.getName());
String filename=fileToCopy.getName();
String nameWithoutExtentionOrIncrement;
String extension = getFileExtension(filename);
if(extension!=null){
extension="."+extension;
int extInd = filename.lastIndexOf(extension);
nameWithoutExtentionOrIncrement = new StringBuilder(filename).replace(extInd, extInd+extension.length(),"").toString();
}
else{
extension="";
nameWithoutExtentionOrIncrement = filename;
}
int c=0;
int indexOfClose = nameWithoutExtentionOrIncrement.lastIndexOf(")");
int indexOfOpen = nameWithoutExtentionOrIncrement.lastIndexOf("(");
if(indexOfClose!=-1 && indexOfClose!=-1 && indexOfClose==nameWithoutExtentionOrIncrement.length()-1 && indexOfClose > indexOfOpen && indexOfOpen!=0){
String possibleNumber = nameWithoutExtentionOrIncrement.substring(indexOfOpen+1, indexOfClose);
try{
c = Integer.parseInt(possibleNumber);
nameWithoutExtentionOrIncrement=nameWithoutExtentionOrIncrement.substring(0, indexOfOpen);
}catch(Exception e){c=0;}
}
while(newFile.exists()){
c++;
String path = destFolderPath + nameWithoutExtentionOrIncrement +"(" + Integer.toString(c) + ")" + extension;
newFile = new File(path);
}
return newFile;
}
public static String getFileExtension(String filename) {
if (filename == null) { return null; }
int lastUnixPos = filename.lastIndexOf('/');
int lastWindowsPos = filename.lastIndexOf('\\');
int indexOfLastSeparator = Math.max(lastUnixPos, lastWindowsPos);
int extensionPos = filename.lastIndexOf('.');
int lastSeparator = indexOfLastSeparator;
int indexOfExtension = lastSeparator > extensionPos ? -1 : extensionPos;
int index = indexOfExtension;
if (index == -1) {
return null;
} else {
return filename.substring(index + 1).toLowerCase();
}
}

Using one regex pattern:
final static Pattern PATTERN = Pattern.compile("(.*?)(?:\\((\\d+)\\))?(\\.[^.]*)?");
String getNewName(String filename) {
if (fileExists(filename)) {
Matcher m = PATTERN.matcher(filename);
if (m.matches()) {
String prefix = m.group(1);
String last = m.group(2);
String suffix = m.group(3);
if (suffix == null) suffix = "";
int count = last != null ? Integer.parseInt(last) : 0;
do {
count++;
filename = prefix + "(" + count + ")" + suffix;
} while (fileExists(filename));
}
}
return filename;
}
The regex pattern explanation:
(.*?) a non greedy "match everything" starting at the beginning
(?:\\((\\d+)\\))? a number in parenthesis (optional)
(?:____________) - is a non capturing group
___\\(______\\)_ - matches ( and )
______(\\d+)____ - matches and captures the one or more digits
(\\.[^.]+)? a dot followed by anything but a dot (optional)

Here's one way of doing it:
String fileName;
File file = new File(fileName);
if(file.exists()) {
int dot = fileName.lastIndexOf('.'), open = fileName.lastIndexOf('('), incr;
boolean validNum = false;
if(fileName.charAt(dot-1) == ')' && open != -1){
String n = fileName.substring(open+1, dot-1);
try {
incr = Integer.parseInt(n);
validNum = true;
} catch(NumberFormatException e) {
validNum = false;
}
}
if(validNum) {
String pre = fileName.substring(0, open+1), post = fileName.substring(0, dot-1);
while(new File(pre + ++incr + post).exists());
fileName = pre + incr + post;
} else {
fileName = fileName.substring(0, dot) + "(1)" + fileName.substring(dot);
}
}

I assume a couple of things:
1) A method called fileExists(String fileName) is available. It returns true if a file with the specified name is already present in the file system.
2) There is a constant called FILE_NAME which in your example case is equal to "text".
if (!fileExists(FILE_NAME)) {
//create file with FILE_NAME.txt as name
}
int availableIndex = 1;
while (true) {
if (!fileExists(currentName)) {
//create file with FILE_NAME(availableIndex).txt
break;
}
availableIndex++;
}

I am not very sure about Android but since its a Java program, you may be able to create File object of the directory in which you want to write.
Once you have this you can see the list of file names already present inside it and other related information. Then you can decide the file name as per your above logic.
File dir = new File("<dir-path>");
if(dir.isDirectory()){
String[] files = dir.list();
for(String fileName : files){
<logic for finding filename>
}
}

If all filenames have an extenstion you could do something like this (just an example you will have to change it to work in your case):
public static void main(String[] args)
{
String test = "test(1)foo.txt";
String test1 = "test(1)foo(1).txt";
Pattern pattern = Pattern.compile("((?<=\\()\\d+(?=\\)\\.))");
Matcher matcher = pattern.matcher(test);
String fileOutput = "";
String temp = null;
int newInt = -1;
while(matcher.find())
{
temp = matcher.group(0);
}
if(temp != null)
{
newInt = Integer.parseInt(temp);
newInt++;
fileOutput = test.replaceAll("\\(\\d+\\)(?=\\.(?!.*\\.))", "(" + newInt + ")");
}
else
{
fileOutput = test;
}
System.out.println(fileOutput);
matcher = pattern.matcher(test1);
fileOutput = "";
temp = null;
while(matcher.find())
{
temp = matcher.group(0);
}
if(temp != null)
{
newInt = Integer.parseInt(temp);
newInt++;
fileOutput = test1.replaceAll("\\(\\d+\\)(?=\\.(?!.*\\.))", "(" + newInt + ")");
}
else
{
fileOutput = test1;
}
System.out.println(fileOutput);
}
Output:
test(1)foo.txt
test(1)foo(2).txt
This uses regex to look for a number in the () right before the last ..
Update
replaceAll() changed to handle case where there is a . after the first (1) in test(1).foo(1).txt.

Changing a string dynamically for file usage

I am trying to figure out how to make a string that I can use to create a file in my java program. I have tried many different ways of doing this, but nothing seems to do what I want.
Here is an example of what I am trying to do:
String fileExt = ".jpg"
for (int i = 0; i < someNumber; i ++){
fileExt = i + fileExt;
}
I want to output something like:
1.jpg
2.jpg
3.jpg
4.jpg
... and so on.
My intention is to use the changed string at every iteration in order to create a new file with it like so : File image = new File (fileExt;

List<File> files = new ArrayList<File>();
String fileExt = ".jpg"
for (int i = 0; i < someNumber; i ++){
File newfile = new File(i + fileExt);
files.add(newfile)
}
A few things here. filext should be absolute path, or the files will be created in your current directory. Keep file references in List for future use.

No matter what you do, the value of fileExt is going to be the last iteration of the loop. Maybe an array will do the trick?
String[] fileExt = new String[20];
for (int i = 0; i < fileExt.length; i++) {
fileExt[i] = i + ".jpg";
}
// view results
for (int i = 0; i < fileExt.length; i++) {
System.out.println(fileExt[i]);
}
// example
File image = new File(fileExt[0]);

Add element in a ArrayList

I am trying to add a new element to an array list but when I print the structure I get the adress in memory. Any idea?
I read the information from a file and I try to put it in a structure Assignatures which is an in numAssignatures and one ArrayList and assignatura has an string with the name and one integer.
public static void llegeixFitxer(Curs[] curs) throws IOException {
FileReader file = new FileReader("assignatures.txt");
BufferedReader reader = new BufferedReader(file);
for (int j=0; j< 5; j++){
curs[j] = new Curs();
curs[j].numAssignatures = Integer.parseInt(reader.readLine());
for (int i = 0; i<curs[j].numAssignatures; i++){
String aux = reader.readLine();
String[] parts = aux.split("-");
String assignaturallegida = parts[0];
int creditsllegits = Integer.parseInt(parts[1].replace(" ",""));
curs[j].addAssignatura(assignaturallegida,creditsllegits);
}
System.out.println(curs[j].getNumAssignatures() + " + " + curs[j].getAssignatures());
}
reader.close();
}
}
I get this:
7 + [model.Assignatura#7eda2dbb, model.Assignatura#6576fe71, model.Assignatura#76fb509a, model.Assignatura#300ffa5d, model.Assignatura#1f17ae12, model.Assignatura#4d405ef7, model.Assignatura#6193b845]
Thank you!!

You have to override the toString() method in your model.Assignatura class.
The default implementation of toString() would print Fully Qualified class name followed by '#' and the object's hash code in hexadecimal format. That's explaining what you are receiving.

Java autogenerate directories if exists

I'm trying to check if a directory exists, if that happens I want to give it another number, for example, if "folderX" exists I want to create a new one called "FolderX1", at the moment I'm just able to do this once since I have it on an if/else statement like this:
File fa = new File(folder);
if(!fa.exists()){
this.folder = folder;
}else{
this.folder = folder+=1;
}
I want do this recursively, If the program detects that "folderX" exists it should jump and check the others (folderX,FolderX1,FolderX2, etc) until it finds one that can be created but i don't know how to do it.

Basically, you need some kind of loop that can determine if the incrementing folder still exists...
File makeMe = new File(folder);
int index = 0;
String master = folder;
while (makeMe.exists()) {
folder = master + (++index);
makeMe = new File(folder);
}
If you're worried about creating an infinite loop, you could place a maximum range...
int maxRange = 100;
File makeMe = new File(folder);
int index = 0;
String master = folder;
while (makeMe.exists() && index < maxRange) {
makeMe = new File(master + (++index));
}
if (index > maxRange) { // || makeMe.exists()
throw new IOException("Could not find free directory");
} else {
// All happy unicorns...
}

String folderPrefix = "folder";
int folderSuffix = 0;
File fa = new File(folderPrefix + folderSuffix);
while (fa.exists()) {
fa = new File(folderPrefix + folderSuffix++);
}