Develop Reference

How to read all files in directory iteratively in Java?

I have a directory on network drive with million of files. If I try to read it with
folder.listFiles()
it will take a lot of time until resulting array will be filled with files.
I would like to receive files by one and printout a progress.
How can I do this in Java?

You might try with DirectoryStream:
Path dir = Paths.get("C:\\"); // directory to list
try (DirectoryStream<Path> stream = Files.newDirectoryStream(dir)) {
for (Path entry: stream) {
System.out.println(entry);
}
} catch (DirectoryIteratorException ex) {
ex.printStackTrace();
} catch (IOException ex) {
ex.printStackTrace();
}
You can also make the DirectoryStream filter files for you if you need to: all you need to do is add a parameter to the Files.newDirectoryStream call:
DirectoryStream<Path> stream = Files.newDirectoryStream(dir, "*.{txt,png,jpg}");

You can use the NIO.2 API:
try (DirectoryStream<Path> directoryStream = Files.newDirectoryStream(Paths.get("/path/to/directory"))) {
for (Path path : directoryStream) {
System.out.println(path.toString());
}
} catch (IOException ex) {}

how to create dynamic paths in java and write the file data in java

I will get dynamic paths from database. Example: 1.xyz/abc/file1.txt
2.pqr/file2.txt
Now I need to append these paths to existing file (eg:/users/rama/) and save that file
my final directory should like /users/rama/xyz/abc/file1.txt
I am able to create directories such as xyz/abc if they don't exist, but the problem is file1.txt is also created as directory instead of file.

I am able to create directories such as xyz/abc if they don't exist,
but the problem is file1.txt is also created as directory instead of
file.
Because you are creating the directories until *.txt. Below an example of code to acheive what you want:
String prefix = "/users/rama/";
String filePath = "xyz/abc/file1.txt";
// concatenation => /users/rama/xyz/abc/file1.txt
String fullPath = prefix.concat(filePath);
PrintWriter writer;
try {
// Getting the directory path : /users/rama/xyz/abc/
int lastIndexOfSlash = fullPath.lastIndexOf("/");
String path = filePath.substring(0, lastIndexOfSlash);
File file = new File(path);
// If /users/rama/xyz/abc/ don't exist then creating it.
if(!file.exists()) {
file.mkdirs();
}
// Creating the file.
writer = new PrintWriter(fullPath, "UTF-8");
writer.println("content");
writer.close();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

Unable to located generated file

I am generating a file using the following syntax
File file = new File("input.txt");
The problem is that it is saying that it is writing to the file but I am not able to locate where the file is created, I searched my entire workspace. The expectation was that it would be created in the same folder as my code which is executing.
Any ideas?
Rest of the code :
File file = new File("input.txt");
// if file doesnt exists, then create it
if (!file.exists()) {
try {
file.createNewFile();
} catch (IOException e) {
e.printStackTrace();
}
}

You could do a sop on the absolute path and you would get the path:
File file = new File("input.txt");
System.out.println("" + file.getAbsolutePath());
if (!file.exists()) {
try {
file.createNewFile();
} catch (IOException e) {
e.printStackTrace();
}
}

When you create file through relative paths, Java uses System.getProperty("user.dir"). So, in your case the full path to file will be System.out.println(System.getProperty("user.dir") + "/input.txt");.

How to copy a zip file in Java

I have a zip file that gets created at runtime that I need to copy to another directory however whenever I run my code I get a DirectoryNotEmptyException. Is there some extra parameter I need to specify to copy into a non-empty directory?
Here's the layout
Path sourceZip = new File(path).toPath();
String destinDir = new File(System.getProperty("user.dir")).getParent();
Path target = Paths.get(destinDir);
try {
Files.copy(sourceZip, target, StandardCopyOption.REPLACE_EXISTING);
} catch (IOException e) //DirectoryNotEmptyException occurs here
{}

the destination needs to contain the full path of the file that will eventually be there.
so you say if you needed to copy /home/dauser/faq.txt to /home/faq.txt
File file = new File(path);
Path sourceZip = file.toPath();
StringBuilder sb = new StringBuilder();
sb.append(new File(System.getProperty("user.dir")).getParent());
sb.append("/");
sb.append(file.getName());
Path target = Paths.get(sb.toString());
try {
Files.copy(sourceZip, target, StandardCopyOption.REPLACE_EXISTING);
} catch (IOException e) //DirectoryNotEmptyException occurs here
{}

i want to overwrite the existing zipfile

i want to overwrite the existing zip file(which mean i add new file in existing zip file) but here show this error (java.util.zip.ZipError: zip END header not found)
private void updateZip(String fileName, String scenarioDirectory){
System.out.println("File Name : " +fileName);
System.out.println("Scenario Directory : " +scenarioDirectory);
String scenarioName ="12345";
Path myFilePath = Paths.get(fileName);
Path zipFilePath = Paths.get(scenarioDirectory);
FileSystem fs;
try {
fs = FileSystems.newFileSystem(zipFilePath,null);
Path fileInsideZipPath = fs.getPath(scenarioName);
Files.copy(myFilePath, fileInsideZipPath);
fs.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

Try this :
if your file exist then delete it ant after save the new.
Or Added a file directly in the zip code since this example https://stackoverflow.com/a/17500924/4017037