Develop Reference

How do I check whether a file is a directory, do the same for its sub directories and their contents recursively and copy them to another location

I am new to programming and I have a problem. I need to check whether a file is a directory or not, if yes need to do the following :
check whether it has contents. Contents can be sub-directories or just files.
need to do the check recursively for every file inside the parent directory
copy each directory and file to another location, preserving the directory structure.
Also need to copy the database entries corresponding to every file/directory to another table
along with the actual files

The process a java.io.File.isDirectory() alters the checking process whether a file with given a specified path name might be a directory or not.
Simply the code returns true if the file is specified by the path name is a directory and false in the opposite case.
import java.io.File;
public class Demo {
public static void main(String[] args) {
try {
File file = new File("demo1.txt");
file.createNewFile();
System.out.println("Is directory? " + file.isDirectory());
} catch(Exception e) {
e.printStackTrace();
}
}
}
output: Is directory? false
let's see how the code is working: a small snippet that mimics the about the code is written down.
try {
File file = new File("demo1.txt");
file.createNewFile();
System.out.println("Is directory? " + file.isDirectory());
} catch(Exception e) {
e.printStackTrace();
}

Specifying file path in java causes FileNotFoundException

This piece of code throws a FileNotFoundException, i'm sure the file exists in my working directory, am i doing something wrong?
private void generateInvoiceNumber(){ //uses reads previous invoice number and increments it.
try {
File invoiceFile = new File("./Invoices/invoiceFile.txt");
FileWriter writer = new FileWriter(invoiceFile,false);
Scanner getter = new Scanner(invoiceFile);
this.invoiceNumber = getter.nextInt();
writer.write(++invoiceNumber);
writer.close();
getter.nextInt();
getter.close();
}
catch (IOException e) {
System.out.println("An error occurred.");
e.printStackTrace();
}
}

My tip:
Print (in your code) the current path location.
Then you can use this path in order to find the exact path you should use in order to access your file.

Maybe you should put more concrete absolute path:
File invoiceFile = Paths.get ("C:","Invoices", "invoiceFile.txt").toFile();
or if you trying to get from current path:
File invoiceFile = Paths.get (".","Invoices", "invoiceFile.txt").toFile();
And you can check your . path:
System.out.println(new File(".").getCanonicalPath());

Which operating system you are using?
It’s better to use paths when you are constructing a path to your file like
File file = Paths.get (".","Invoices", "invoice.txt").toFile();
corrected " symbols and default root "." which is your folder where app started.

reading an external file using TextIO

I don't understand how to use TextIO's readFile(String Filename)
Can someone please explain how can I read an external file?
public static void readFile(String fileName) {
if (fileName == null) // Go back to reading standard input
readStandardInput();
else {
BufferedReader newin;
try {
newin = new BufferedReader( new FileReader(fileName) );
}
catch (Exception e) {
throw new IllegalArgumentException("Can't open file \"" + fileName + "\" for input.\n"
+ "(Error :" + e + ")");
}
if (! readingStandardInput) { // close current input stream
try {
in.close();
}
catch (Exception e) {
}
}
emptyBuffer(); // Added November 2007
in = newin;
readingStandardInput = false;
inputErrorCount = 0;
inputFileName = fileName;
}
}

I had to use TextIO for a school assignment and I got stuck on it too. The problem I had was that using the Scanner class I could just pass the name of the file as long as the file was in the same folder as my class.
Scanner fileScanner = new Scanner("data.txt");
That works fine. But with TextIO, this won't work;
TextIO.readfile("data.txt"); // can't find file
You have to include the path to the file like this;
TextIo.readfile("src/package/data.txt");
Not sure if there is a way to get it to work like the Scanner class or not, but this is what I've been doing in my course at school.

The above answer (about using the correct file name) is correct, however, as a clarification, make sure that you actually use the proper file path. The file path suggested above, i.e. src/package/ will not work in all circumstances. While this will be obvious to some, for those of you who need clarification, keep reading.
For example (and I use NetBeans), if you have already moved the file into NetBeans, and the file is already in the folder you want it to be in, then right click on the folder itself, and click 'properties'. Then expand the 'file path' section by clicking on the three dots next to the hidden file path. You will see the actual file path in its entirety.
For example, if the entire file path is:
C:\Users..\NetBeansProjects\IceCream\src\icecream\icecream.dat
Then, in the java code file itself, you can write:
TextIo.readfile("src/icecream/icecream.dat");
In other words, make sure you include the words 'src' but also everything that follows the src as well. If it's in the same folder as the rest of the files, you won't need anything prior to the 'src'.

Java formatter - setting file directory

i am trying to create a text file in a folder (called AMCData). The file is called "File" (for the sake of this example).
I have tried using this code:
public static void OpenFile(String filename)
{
try
{
f = new Formatter("AMCData/" + filename + ".txt");
}
catch(Exception e)
{
System.out.println("error present");
}
}
But before i get the chance to even place any text in it, the catch keeps being triggered..
Could anyone inform me why this is occuring?
more information:
The folder does not exist, i was hoping it would automatically create it
If it doesn't automatically create folders, could you please link me to how to do so?

You're right, a Formatter(String) constructor needs the file to be present or createable. The most likely reason why a file cannot be created is that it references a folder that itself doesn't exist, so you should use the File.mkdirs() method, like this:
new File("AMCData").mkdirs();

Java's createNewFile() - will it also create directories?

I've got a conditional to check if a certain file exists before proceeding (./logs/error.log). If it isn't found I want to create it. However, will
File tmp = new File("logs/error.log");
tmp.createNewFile();
also create logs/ if it doesn't exist?

No.
Use tmp.getParentFile().mkdirs() before you create the file.

File theDir = new File(DirectoryPath);
if (!theDir.exists()) theDir.mkdirs();

File directory = new File(tmp.getParentFile().getAbsolutePath());
directory.mkdirs();
If the directories already exist, nothing will happen, so you don't need any checks.

Java 8 Style
Path path = Paths.get("logs/error.log");
Files.createDirectories(path.getParent());
To write on file
Files.write(path, "Log log".getBytes());
To read
System.out.println(Files.readAllLines(path));
Full example
public class CreateFolderAndWrite {
public static void main(String[] args) {
try {
Path path = Paths.get("logs/error.log");
Files.createDirectories(path.getParent());
Files.write(path, "Log log".getBytes());
System.out.println(Files.readAllLines(path));
} catch (IOException e) {
e.printStackTrace();
}
}
}

StringUtils.touch(/path/filename.ext) will now (>=1.3) also create the directory and file if they don't exist.

No, and if logs does not exist you'll receive java.io.IOException: No such file or directory
Fun fact for android devs: calls the likes of Files.createDirectories() and Paths.get() would work when supporting min api 26.