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Add suffix to filename if file already exist instead of overwriting it

I'm saving an uploaded file as below:
UploadItem item = event.getUploadItem();
File dir = new File("D:/FileUpload");
if (!dir.exists()) {
dir.mkdir();
}
File bfile = new File("D:/FileUpload" + "/" + item.getFileName());
OutputStream outStream = new FileOutputStream(bfile);
outStream.write(item.getData());
outStream.close();
But my question is when upload once file same old file in folder D:/FileUpload. In above function it will delete old file. Example first time, i upload file : test.doc (old file). Then i upload another file with same name : test.doc (new file). At folder FileUpload will has one file is test.doc (new file). I want function will process similar in window OS is : new file will be test (2).doc. How can i process it ? And all cases : D:/FileUpload have many file : test.doc, test (1).doc, test (2).doc, test (a).doc,...... I think we just check with format ....(int).doc. That new file will be :
test (3).doc (ignore test(a).doc)

Maybe you're looking for something like this? I list the files in your directory, compare the names of each to the name of your file. If the names match, increment a count. Then, when you come to create your file, include the count in its name.
UploadItem item = event.getUploadItem();
File dir = new File("D:/FileUpload");
if (!dir.exists()) {
dir.mkdir();
}
String [] files = dir.list();
int count = 0;
for(String file : files) {
if (file.startsWith(item.getFileName()) {
count++;
}
}
File bfile = new File("D:/FileUpload" + "/" + item.getFileName() + "(" + count + ")");
OutputStream outStream = new FileOutputStream(bfile);
outStream.write(item.getData());
outStream.close();

merging two strings to shape a file path

assuming that we have a folder with path:
path="C:\\Users\\me\\Desktop\\here"
also, consider a File[] named readFrom has different files. as an example, consider following path which refering to a file:
C:\\Users\\me\\Desktop\\files\\1\\sample.txt"
my question is, how can i have a string with following value:
String writeHere= "C:\\Users\\me\\Desktop\\here\\files\\1\\sample.txt"
EDIT
I should have mentioned that this path is unknown, we need first to read a file and get its path then write it into another folder, so for the path of writing I need writeHere as input. in conclusion , the answer should contains the way to get the path from the file too.

String s1="C:\\Users\\me\\Desktop\\here";
String s2="C:\\Users\\me\\Desktop\\files\\1\\sample.txt";
String s3=s2.substring(s2.indexOf("\\files"));
System.out.println(s1+s3);
OUTPUT
C:\Users\me\Desktop\here\files\1\sample.txt
To get Absolute Path of file
File f=new File("C:\\Users\\me\\Desktop\\files\\1\\sample.txt");
System.out.println(f.getAbsolutePath());

Split the into arrays and merge the path with split-ted string
String path="C:\\Users\\me\\Desktop\\here";
String [] splt = yourPath.split("\\");
finalPath = path + "\\" + splt[3] + "\\" + splt[4] + "\\" + splt[5];
yourPath is the path refering to a file
Changing the folder's path
File afile =new File("C:\\Users\\me\\Desktop\\files\\1\\sample.txt");
afile.renameTo(new File(finalPath))

If you just need the String and do not need to read the file, use string concatenation with is just str1 + str2. If you need the File object create a base File object on the initial path and then two new File objects from that:
File path = new File("C:\\Users\\me\\Desktop\\here");
String[] files = { "files\\1\\sample.txt", "files\\3\\this.avi" };
for (filename in files) {
File f = new File(path, filename);
...
}
Oh, I think I see better what you want to do. You want to "reparent" the files:
// Note:
// newParent I assume would be a parameter, not hardcoded
// If so, there is no hardcoding of the platform specific path delimiter
// the value, start, is also assumed to be a parameter
File newParent = new File("C:\\Users\\me\\Desktop\\here");
File[] readFrom = ...;
for (File f in readFrom) {
String[] parts = f.list();
String[] needed = Arrays.copyOfRange(parts, start, parts.length);
File newFile = new File(newParent);
for (String part in needed) {
newFile = new File(newFile, part);
}
...
}

I think you could do something like:
String name = "Rafael";
String lastname = " Nunes";
String fullname = name + lastname;
Here you can see the string concatenation working, and you can often visit the Java documentation.

Add index to filename for existing file (file.txt => file_1.txt)

I want to add an index to a filename if the file already exists, so that I don't overwrite it.
Like if I have a file myfile.txt and same time myfile.txt exists in destination folder - I need to copy my file with name myfile_1.txt
And same time if I have a file myfile.txt, but destintation folder contains myfile.txt and myfile_1.txt - generated filename has to be myfile_2.txt
So the functionality is very similar to the creation of folders in Microsoft operating systems.
What's the best approach to do that?

Using commons-io:
private static File getUniqueFilename( File file )
{
String baseName = FilenameUtils.getBaseName( file.getName() );
String extension = FilenameUtils.getExtension( file.getName() );
int counter = 1
while(file.exists())
{
file = new File( file.getParent(), baseName + "-" + (counter++) + "." + extension );
}
return file
}
This will check if for instance file.txt exist and will return file-1.txt

You might also benefit from using the apache commons-io library. It has some usefull file manipulation methods in class FileUtils and FilenameUtils.

Untested Code:
File f = new File(filename);
String extension = "";
int g = 0;
int i = f.lastIndexOf('.');
extension = fileName.substring(i+1);
while(f.exists()) {
if (i > 0)
{ f.renameTo(f.getPath() + "\" + (f.getName() + g) + "." + extension); }
else
{ f.renameTo(f.getPath() + "\" + (f.getName() + g)); }
g++;
}

Try this link partly answers your query.
https://stackoverflow.com/a/805504/1961652
DirectoryScanner scanner = new DirectoryScanner();
scanner.setIncludes(new String[]{"**/myfile*.txt"});
scanner.setBasedir("C:/Temp");
scanner.setCaseSensitive(false);
scanner.scan();
String[] files = scanner.getIncludedFiles();
once you have got the correct set of files, append a proper suffix to create a new file.

How to create multiple directories given the folder names

I have a list of files, the names of these files are are made of a classgroup and an id (eg. science_000000001.java)
i am able to get the names of all the files and split them so i am putting the classgroups into one array and the ids in another.. i have it so that the arrays cant have two of the same values.
This is the problem, i want to create a directory with these classgroups and ids, an example:
science_000000001.java would be in science/000000001/science_000000001.java
science_000000002.java would be in science/000000002/science_000000002.java
maths_000000001.java would be in maths/000000001/maths_000000001.java
but i cannot think of a way to loop through the arrays correctly to create the appropriate directories?
Also i am able to create the folders myself, its just getting the correct directories is the problem, does anyone have any ideas?

Given:
String filename = "science_000000001.java";
Then
File fullPathFile = new File(filename.replaceAll("(\\w+)_(\\d+).*", "$1/$2/$0"));
gives you the full path of the file, in this case science/000000001/science_000000001.java
If you want to create the directory, use this:
fullPathFile.getParentFile().mkdirs();

The above answer is really good for creating new files with that naming convention. If you wanted to sort existing files into their relative classgroups and Ids you could use the following code:
public static void main(String[] args) {
String dirPath = "D:\\temp\\";
File dir = new File(dirPath);
// Get Directory Listing
File[] fileList = dir.listFiles();
// Process each file
for(int i=0; i < fileList.length; i++)
{
if(fileList[i].isFile()) {
String fileName = fileList[i].getName();
// Split at the file extension and the classgroup
String[] fileParts = fileName.split("[_\\.]");
System.out.println("One: " + fileParts[0] + ", Two: " + fileParts[1]);
// Check directory exists
File newDir = new File(dirPath + fileParts[0] + "\\" + fileParts[1]);
if(!newDir.exists()) {
// Create directory
if(newDir.mkdirs()) {
System.out.println("Directory Created");
}
}
// Move file into directory
if(fileList[i].renameTo(new File(dirPath + fileParts[0] + "\\" + fileParts[1] + "\\" + fileName))) {
System.out.println("File Moved");
}
}
}
}
Hope that helps.

FTP client - listfiles

I am unable to get the exact file list using FTPClient. Sample code as below :
FTPClient client = new FTPClient();
client.connect("x.x.x.x");
client.login("abcd", "abcd");
FTPFile[] ftpFiles = client.listFiles();
for (FTPFile ftpFile : ftpFiles) {
System.out.println("FTPFile: " + ftpFile.getName());
}
I tried to set to PASV mode using enterLocalPassiveMode()/enterRemotePassiveMode()/pasv(). But, it doesnt work.
Please also check Apache Commons FTPClient.listFiles ..
Thank you

I don't know what files is, but you're getting the results of client.listFiles in ftpFiles, and not in files. Then in your for loop you go over files.

Try this.
String[] fileFtp = client.listNames();//if it is directory. then list of file names
//download file
for (int i =0;i<fileFtp.length;i++) {
String fileName = fileFtp[i];
OutputStream out = new FileOutputStream(new File("local temp file name"));
if (!client.retrieveFile(fileName, out)) {
sysout("Could not download the file. "+ fileName);
} else {
sysout("Downloaded file # : "+localFileName);
}
}
This should work.
Thanks.