I'm running Windows and I'm trying to refer to a directory. My function starts off like this:
File file = new File("C:\\somedir\\report");
if (!file.exists()) {
file.mkdirs();
}
doStuffWith(file);
I got a NullPointerException within the doStuffWith function, when I tried to call listFiles. Well I looked in C:\somedir and what did I find - there is a file called "report" with no extension, and also a directory called "report"! What seemed to happen was that the file object was referring to the report file rather than the directory. How do I make sure that I am referring to the directory and not the file?
one way to go about is to pass the file object corresponding to "C:\somedir" to the method and inside the method, do a listFiles() and walk through the contents, each time checking for file name and if it is "report", do a isDirectory(). proceed with actual processing when this returns true.
i think there is a isDirectory() method that will tell you if it is a directory
--EDIt
that's what I get for being up so early. I ran your code locally and it works fine for me. Was able to create new files, read directory contents, etc. What else are you trying to do?
I don't understand the problem this works fine for me:
public class MkDir {
static void doStuff(File dir) {
if ( dir.isDirectory() ) {
File[] listFiles = dir.listFiles();
for ( File f : listFiles ) {
System.out.println( f.getName() );
}
}
}
public static void main(String[] args) {
File file = new File( "C:\\dev\\rep2\\rep" );
if ( !file.exists() ) {
file.mkdirs();
}
doStuff( file );
}
}
Check if your file system has had case sensitivity enabled (HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\kernel\ dword:ObCaseInsensitive in the registry.)
If so, you may be getting bitten by a case-related issue. One way to check:
String someName = "./nameNotUsedYet";
boolean first = new File(someName).mkdirs();
boolean second = new File(someName.toUpperCase()).mkdirs();
System.out.println("first = " + first + ", second = " + second);
If both mkdirs() calls succeeded, you know you have a case related complication. If so, ensure that you get the case for "C:\somedir\report" exactly right.
Related
I have been working on a project where I will get a filename from API and have to check whether the file is present in the device and play it.
I am getting Screenshot.jpg as filename from API and under the same name a file is present in my storage.
But when I used the piece of code, I have been returned false. I have checked with other codes also.
public boolean isFilePresent(String fileName) {
String path = this.getFilesDir().getAbsolutePath() + "/" + fileName;
File file = new File(path);
return file.exists();
}
where am I going wrong? Any help would be greatly appreciated!
Probably, what you do wrong is using this.getFilesDir().
Instead, use Environment.getExternalStorageDirectory().toString() for example, it's all dependant on where your file is.
Like I said before, debug it yourself, print (or present a toast) with the 'expected' file path, then verify it doesn't exist
Try something like that :
public boolean isFilePresent(Context context, String fileName) {
File dirFiles = context.getFilesDir();
File[] filesArray = dirFiles.listFiles();
for (File file : filesArray) {
if (file.getName().equals(fileName)) {
return true;
}
}
return false;
}
Use Environment.getExternalStorageDirectory() this is how you get the files directory
then you will add your files path after it, so you should do something like this
if(!new File(Environment.getExternalStorageDirectory().toString()+"/myFolder/"+"myFile").exist())
{
// file is not exist
}
remember to check the runtime permission because it's a special permission
We need to call file.exists() before file.delete() before we can delete a file E.g.
File file = ...;
if (file.exists()){
file.delete();
}
Currently in all our project we create a static method in some util class to wrap this code. Is there some other way to achieve the same , so that we not need to copy our utils file in every other project.
Starting from Java 7 you can use deleteIfExists that returns a boolean (or throw an Exception) depending on whether a file was deleted or not. This method may not be atomic with respect to other file system operations. Moreover if a file is in use by JVM/other program then on some operating system it will not be able to remove it. Every file can be converted to path via toPath method . E.g.
File file = ...;
boolean result = Files.deleteIfExists(file.toPath()); //surround it in try catch block
file.delete();
if the file doesn't exist, it will return false.
There's also the Java 7 solution, using the new(ish) Path abstraction:
Path fileToDeletePath = Paths.get("fileToDelete_jdk7.txt");
Files.delete(fileToDeletePath);
Hope this helps.
Apache Commons IO's FileUtils offers FileUtils.deleteQuietly:
Deletes a file, never throwing an exception. If file is a directory, delete it and all sub-directories.
The difference between File.delete() and this method are:
A directory to be deleted does not have to be empty.
No exceptions are thrown when a file or directory cannot be deleted.
This offers a one-liner delete call that won't complain if the file fails to be deleted:
FileUtils.deleteQuietly(new File("test.txt"));
I was working on this type of function, maybe this will interests some of you ...
public boolean deleteFile(File file) throws IOException {
if (file != null) {
if (file.isDirectory()) {
File[] files = file.listFiles();
for (File f: files) {
deleteFile(f);
}
}
return Files.deleteIfExists(file.toPath());
}
return false;
}
if you have the file inside a dirrectory called uploads in your project. bellow code can be used.
Path root = Paths.get("uploads");
File existingFile = new File(this.root.resolve("img.png").toUri());
if (existingFile.exists() && existingFile.isFile()) {
existingFile.delete();
}
OR
If it is inside a different directory this solution can be used.
File existingFile = new File("D:\\<path>\\img.png");
if (existingFile.exists() && existingFile.isFile()) {
existingFile.delete();
}
Use the below statement to delete any files:
FileUtils.forceDelete(FilePath);
Note: Use exception handling codes if you want to use.
Use Apache Commons FileUtils.deleteDirectory() or FileUtils.forceDelete() to log exceptions in case of any failures,
or FileUtils.deleteQuietly() if you're not concerned about exceptions thrown.
Generally We create the File object and check if File Exist then delete.
File f1 = new File("answer.txt");
if(f1.exists()) {
f1.delete();
}
OR
File f2 = new File("answer.txt");
f2.deleteOnExit();
If you are uses the Apache Common then below are the option using which you can delete file and directory
File f3 = new File("answer.txt");
FileUtils.deleteDirectory(f3);
This method throws the exception in case of any failure.
OR
File f4 = new File("answer.txt");
FileUtils.deleteQuietly(f4);
This method will not throw any exception.
This is my solution:
File f = new File("file.txt");
if(f.exists() && !f.isDirectory()) {
f.delete();
}
File xx = new File("filename.txt");
if (xx.exists()) {
System.gc();//Added this part
Thread.sleep(2000);////This part gives the Bufferedreaders and the InputStreams time to close Completely
xx.delete();
}
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'.
So I am trying to copy one file from one place to the other using the solution found here :
Copying files from one directory to another in Java
My code creates the new directory but cant seem to find the file ,even though the landedtitlesFile is pointing to the proper path and file. I always get my "blast" comment in case you were wondering if my program gets to the end of the method.
Thank you for your time and patience.
private File landedtitlesFile = new File("C:\\Program Files (x86)\\Steam\\SteamApps\\common\\Crusader Kings II\\common\\landed_titles\\landed_titles.txt");
private String modPath = "C:\\Users\\Bernard\\Documents\\Paradox Interactive\\Crusader Kings II\\mod\\viking";
public void createCopyLandedTitles(Boolean vanilla){
if (vanilla == true) {
File dir = new File(modPath + "\\common\\landed_titles");
dir.mkdir();
try{
FileUtils.copyFile(landedtitlesFile,dir);
}
catch (IOException e ){
System.out.println("blast");
}
}
copyFile expects the second parameter to be the destination file, not a destination directory. You need to give it the target name of the file within that directory:
FileUtils.copyFile(
landedtitlesFile,
new File(dir, landedtitlesFile.getName());
Exception objects generally contain some information on the cause. If you print out the exception with e.printStackTrace(); (or rethrow it up the stack with throw new RuntimeException(e);) then you will be able to see what it says.
Good Day!
I wrote the method in Java which must search files in folders and do some operations with them.
So the problem is that when I try to check what I have (file or dir) I receive nothing in both cases! But as i can see paths look correct.
How can I fix this problem?
Here is the code:
public void searchInDir(){
File inputFile = new File( this.fileName );
String[] namesOfFilesDir = inputFile.list();
for ( int i = 0; i < namesOfFilesDir.length; i++ )
{
String normalPath = this.getNormalPath(inputFile.getCanonicalPath()); //C:\User -> C:\\User
// Two separators for correcting path to file
String pathToCurrentFile = normalPath + File.separator + File.separator + namesOfFilesDir[i];
File f = new File( pathToCurrentFile, namesOfFilesDir[i] );
System.out.printf("FileName=%s, Path=[%s]\n", namesOfFilesDir[i], pathToCurrentFile);
System.out.println(f.isDirectory());//False
System.out.println(f.isFile());//False too
//Some other code
}
}
For example this.fileName consists path to folder ( and this folder consists one folder and 2 files).
I got next:
FileName=Readme.txt, Path=[C:\\workspace\\Grep\\t\\Readme.txt]
false
false
FileName=t2, Path=[C:\\workspace\\Grep\\t\\t2]
false
false
FileName=test.txt, Path=[C:\\workspace\\Grep\\t\\test.txt]
false
false
Ok. Program says that.
Lets print next code as an example.
File f = new File("C:\\workspace\\Grep\\t\\Readme.txt");
System.out.println(f.isFile());
Program will print ”True”.
This part makes no sense:
String pathToCurrentFile = normalPath + File.separator + File.separator + namesOfFilesDir[i];
File f = new File( pathToCurrentFile, namesOfFilesDir[i] );
Even if we forget about the double separator for the time being, it makes no sense to first construct the file name by adding namesOfFilesDir[i], then construct a File() object using the two-argument constructor which basically adds namesOfFilesDir[i] once more. Try printing f.getAbsolutePath() and you'll see what I mean. It should have probably been something like:
File f = new File( normalPath, namesOfFilesDir[i] );
Probably the file doesn't exist, so it is neither a file nor a directory. Try printing the output of f.exists() as well.
Did you notice the duplicate file separator in your path?
I think that perhaps your paths are not correct. Both isFile() and isDirectory() only return true if the file/directory actually exists. Have you tried calling exists() on the file? Also, I'm suspicious of what your getNormalPath() method is doing - I think it might be mangling the filenames.
The 1st System.out.println is missleading!
It would have been better to output the path of f.
Anyway, according the output:
FileName=Readme.txt, Path=[C:\workspace\Grep\t\Readme.txt]
f will be C:\workspace\Grep\t\Readme.txt\Readme.txt
that is, namesOfFilesDir[i] is being appended twice!
It would be easier/better to work just with instances of File directly:
File inputFile = new File(this.fileName);
File[] files = inputFile.listFiles();
for (File f : files) {
System.out.printf("FileName=%s, Parent=[%s]\n", f.getName(), f.getParent());
System.out.println(f.isDirectory());
System.out.println(f.isFile());
//Some other code
}