I have this piece of code in my project:
String readFile() {
String pathname = saveDirectory + fileName + ".txt";
String content = "";
File f = new File(pathname);
if (f.exists() && !f.isDirectory()) {
try {
content = new String(Files.readAllBytes(Paths.get(pathname)));
}
catch (IOException e) { }
}
return content;
}
There are no errors, the aplication runs just right, but the content variable never has any text in it and I'm sure that the txt file has text in it!
I've already tried different ways to read the text file (with BufferedReader, Scanner, FileInputStream and FileReader) but none of them worked.
Ps. I'm almost sure that the problem isn't in the pathname variable since I've tried to open the file via code (with Runtime) and it opened the right file normally.
Ok, I tried adding the e.printStackTrace(); but there is still no errors, and it's not missing a / between the directory and the fileName, i've already added in the \\ in the directory variable.
Could you be forgetting the / between the directory and the file name? Print the content of pathname and see.
Or better: debug your code and see what happens.
It looks like you're opening the file once (File f = new File(pathname);), then trying to read it without using the file object you created. You're probably getting an IOException because Files.readAllBytes(Paths.get(pathname)) can't open the file while f has it open.
Related
This is currently what I have to delete the file but it's not working. I thought it may be permission problems or something but it wasn't. The file that I am testing with is empty and exists, so not sure why it doesn't delete it.
UserInput.prompt("Enter name of file to delete");
String name = UserInput.readString();
File file = new File("\\Files\\" + name + ".txt");
file.delete();
Any help would be GREATLY appreciated!
I now have:
File file = new File(catName + ".txt");
String path = file.getCanonicalPath();
File filePath = new File(path);
filePath.delete();
To try and find the correct path at run time so that if the program is transferred to a different computer it will still find the file.
The problem could also be due to any output streams that you have forgotten to close. In my case I was working with the file before the file being deleted. However at one place in the file operations, I had forgotten to close an output stream that I used to write to the file that was attempted to delete later.
Be sure to find out your current working directory, and write your filepath relative to it.
This code:
File here = new File(".");
System.out.println(here.getAbsolutePath());
... will print out that directory.
Also, unrelated to your question, try to use File.separator to remain OS-independent. Backslashes work only on Windows.
I got the same problem! then realized that my directory was not empty. I found the solution in another thread: not able to delete the directory through Java
/**
* Force deletion of directory
* #param path
* #return
*/
static public boolean deleteDirectory(File path) {
if (path.exists()) {
File[] files = path.listFiles();
for (int i = 0; i < files.length; i++) {
if (files[i].isDirectory()) {
deleteDirectory(files[i]);
} else {
files[i].delete();
}
}
}
return (path.delete());
}
Try closing all the FileOutputStream/FileInputStream you've opened earlier in other methods ,then try deleting ,worked like a charm.
I suspect that the problem is that the path is incorrect. Try this:
UserInput.prompt("Enter name of file to delete");
String name = UserInput.readString();
File file = new File("\\Files\\" + name + ".txt");
if (file.exists()) {
file.delete();
} else {
System.err.println(
"I cannot find '" + file + "' ('" + file.getAbsolutePath() + "')");
}
If you want to delete file first close all the connections and streams.
after that delete the file.
In my case it was the close() that was not executing due to unhandled exception.
void method() throws Exception {
FileInputStream fis = new FileInputStream(fileName);
parse(fis);
fis.close();
}
Assume exception is being thrown on the parse(), which is not handled in this method and therefore the file is not closed, down the road, the file is being deleted, and that delete statement fails, and do not delete.
So, instead I had the code like this, then it worked...
try {
parse(fis);
}
catch (Exception ex) {
fis.close();
throw ex;
}
so basic Java, which sometimes we overlook.
As other answers indicate, on Windows you cannot delete a file that is open. However one other thing that can stop a file from being deleted on Windows is if it is is mmap'd to a MappedByteBuffer (or DirectByteBuffer) -- if so, the file cannot be deleted until the byte buffer is garbage collected. There is some relatively safe code for forcibly closing (cleaning) a DirectByteBuffer before it is garbage collected here: https://github.com/classgraph/classgraph/blob/master/src/main/java/nonapi/io/github/classgraph/utils/FileUtils.java#L606 After cleaning the ByteBuffer, you can delete the file. However, make sure you never use the ByteBuffer again after cleaning it, or the JVM will crash.
I want to convert a text file to a html file and then open it with a browser. I try to use file.renameTo() to rename the text file's extension to .html but the rename attempt always fails and file.renameTo() always returns false. Therefore, when I try to open the file in the below method, the file is opened in notepad.
file declaration:
private File file;
file declaration in constructor:
file = new File("D:/dc1000/Project/webPage.txt");
file.getParentFile().mkdirs();
method that doesn't work:
public void compileWebpage(){
File file2 = new File("D:/dc1000/Project/CompiledWebpage.html");
file2.getParentFile().mkdirs();
addFileTags("end"); //add ending tags like </body>
boolean success = true;
try{
success = file.renameTo(file2);
}catch (Exception e){
System.out.println(e);
}
if(!success){
System.out.println("webPage compilation failed.");
}
Desktop desktop = Desktop.getDesktop();
try{
desktop.browse(file.toURI());
}catch (IOException e){
e.printStackTrace();
}
}
No exceptions are thrown, "Webpage compilation failed" is printed to the console and then notepad opens the file. The file looks like this when opened in notepad:
<html>
<head>
</head>
<body>
<p>hi</p>
</body>
</html>
Why does File.renameTo() always fail? How can I open this text file in a browser as a html file?
Well, off hand it's rather hard to tell without truly knowing what the addFileTag() method is doing. The only reason I can think of is that the webPage.txt file is still open for either read or write operations.
Your code has accessed the file but never closed it again. You can't rename a file that is open. I would have to assume this is in fact done somewhere within the addFileTag() method.
Because your call to the File.renameTo() method was unsuccessful the "webPage.txt" text file was never renamed to "CompiledWebpage.html" so in essence the "CompiledWebpage.html" file simply does not exist within the system. This however is not the reason why the Windows NotePad application is opening your file instead of the expected default Web Browser:
To begin with the File object variable so conveniently named 'file' was declared and initialized to be related to the "D:/dc1000/Project/webPage.txt" text file and it always will be since it's Class global unless of course that relationship is changed somewhere within your code. To be blunt... it's not and I guess it's a good thing for now because IF your File Rename was successful you would have simply gotten an FileNotFound Exception because the text file related to the 'file' variable would no longer exist due to the simple fact that it was renamed.
What you really want to pass to the DeskTop.browse() method is the File object 'file2' variable which is related to the "D:/dc1000/Project/CompiledWebpage.html" text file. Mind you, you'll still get an FileNotFound Exception because the File.renameTo() method had failed. So you definitely want to make sure you have success here.
Whatever...Why did the Windows NotePad application open instead of the Web Browser?
Here's why:
The Operating System File Associations is what determines which application will open the file when using the DeskTop.browse() method. In the Windows Operating System, by default, a file with the file name extension of ".txt" is automatically opened and displayed within NotePad, a file with the file name extension of ".docx" is automatically opened and displayed in MS Office WORD, a file with the file name extension of ".html" is opened and displayed within the default Web Browser. I think you get the idea here.
Because the 'file' variable is still related to the file "D:/dc1000/Project/webPage.txt" and because the File.renameTo() method failed, Windows simply seen the .txt file extension and displayed the file (as stipulated within the 'file' variable) to NotePad.
So...How do I get all this to actually Work!?
Well, if I may be so bold, do this instead:
Place this somewhere in your code, a button action event or whatever:
String sourceFile = "D:/dc1000/Project/webPage.txt";
String destinationFile = "D:/dc1000/Project/CompiledWebpage.html";
boolean success = CompileToWebPage(sourceFile, destinationFile, "This is My Head Text");
if (success) {
System.out.println("Text File Successfully Compiled!");
}
else {
System.out.println("Text File Compilation FAILED!");
}
//Display our new file in the web Browser...
try {
File htmlFile = new File(destinationFile);
Desktop.getDesktop().browse(htmlFile.toURI());
} catch (IOException ex) {}
Here is a new CompileToWebPage() method:
private static boolean CompileToWebPage(final String sourcefilePath,
final String destinationFilePath, String... headText) {
// headText is OPTIONAL.
String headTxt = "";
if (headText.length != 0) { headTxt = headText[0]; }
//Read sourcefilePath file data into a String ArrayList...
BufferedReader input;
try {
input = new BufferedReader(new FileReader(sourcefilePath));
if (!input.ready()) { throw new IOException(); }
}
catch (FileNotFoundException ex) {
JOptionPane.showMessageDialog(null,"CompileToWebPage() Method Error!\n\nThe supplied "
+ "file path was not found!\n\n" + sourcefilePath, "File NotFound",
JOptionPane.ERROR_MESSAGE);
return false;
}
catch (IOException ex) {
JOptionPane.showMessageDialog(null,"CompileToWebPage() Method Error!\n\nThe supplied "
+ "file is not ready to be read!\n\n" + ex.getMessage(), "File Not Ready",
JOptionPane.ERROR_MESSAGE);
return false;
}
// Place required HTML Tags into String ArrayList
ArrayList<String> txt = new ArrayList<>();
txt.add("<html>");
txt.add("<head>");
txt.add(headTxt);
txt.add("</head>");
txt.add("<body>");
// Read each line of the source text File and add
// them to our String ArrayList...
try {
String str;
while((str = input.readLine()) != null){
txt.add("<p>" + str + "</p>");
}
input.close();
}
catch (IOException ex) {
JOptionPane.showMessageDialog(null,"CompileToWebPage() Method Error!\n\n"
+ "There was a problem reading the source Text from file!\n\n"
+ ex.getMessage(), "File Read Error", JOptionPane.ERROR_MESSAGE);
return false;
}
// Place our HTML finishing Tags into our String ArrayList...
txt.add("</body>");
txt.add("</html>");
// Write the String ArrayList to our supplied Destination
// File Path...
try {
FileWriter fw = new FileWriter(destinationFilePath);
Writer output = new BufferedWriter(fw);
for (int i = 0; i < txt.size(); i++) {
// Some Windows applications (such as NotePad require
// the \r tag for a new line to actually be accomplished
// within a text file.
output.write(txt.get(i) + "\r\n");
}
output.close();
return true;
}
catch (IOException ex) {
JOptionPane.showMessageDialog(null,"CompileToWebPage() Method Error!\n\n"
+ "There was a problem writing the Compiled Web Text to file!\n"
+ "Ensure that permissions are properly set.\n\n" + ex.getMessage(),
"File Write Error", JOptionPane.ERROR_MESSAGE);
return false;
}
}
Well, I hope this has helped you somewhat or at the very least been entertaining.
This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 7 years ago.
I keep getting a java.lang.NullPointerException when trying to open a txt file in eclipse. Basically, this is a main menu, and when you click the "Rules" button, the rules text file should open. Currently, the txt file is located in a package called "Resources" (which is where all of the other img files I've used in making the game are). Here's the code:
private List<String> readFile(String filename)
{
List<String> records = new ArrayList<String>();
try
{
BufferedReader buff = new BufferedReader(new InputStreamReader(
Configuration.class.getResourceAsStream(filename)));
String line;
while ((line = buff.readLine()) != null)
{
records.add(line);
}
buff.close();
return records;
}
catch (Exception e)
{
System.err.format("Exception occurred trying to read '%s'.", filename);
e.printStackTrace();
return null;
}
}
//action performed
public void actionPerformed(ActionEvent ae) {
JButton b = (JButton)ae.getSource();
if( b.equals(newGameButton) )
{
flag = true;
controller.startGame();
buttonPressed = "newGameBtn";
}
if(b.equals(quitButton))
{
System.exit(0);
}
if(b.equals(ruleButton)){
readFile("../resource/riskRules.txt");
}
}
Appreciate the help!
If "Resources" it's marked as resource in Eclipse. The txt file should be copied to your class path when you build.
As per what I can guess from your code you should be doing something like
Configuration.class.getResourceAsStream("riskRules.txt")
Since your file will be at the root level of your class path.
If for example the file is withing a dir called "text" in your resources you would use something like
Configuration.class.getResourceAsStream("text/riskRules.txt")
There needs to be some level of rudimentary error checking on the result returned from getResourceAsStream before you attempt to use it. Is there a reason you're using getResourceAsStream instead of getResource? If the file exists on disk (I see from your OP that it's because it's in a package, and may not physically exist on the disk), then you can just use that to return the path to it, and create a file object from it.
String path = "/path/to/resource"; // note the leading '/' means "search from root of classpath"
URL fileUrl = getClass().getResource(path);
if (fileUrl != null ) {
File f = new File(fileUrl.toURI());
BufferedReader = new BufferedReader(new FileReader(f));
// do stuff here...
}
else {
// file not found...
}
If you need to pull the file out of the JAR archive, then you can do this:
String path = "/path/to/resource"; // note the leading '/' means "search from root of classpath"
InputStream is = getClass().getResourceAsStream(path);
if (is != null ) {
BufferedReader = new BufferedReader(new InputStreamReader(is));
// do stuff here...
}
else {
// file not found...
}
In the event your resource is not found, you will avoid the NPE and you can properly account for the fact that it's missing.
Note that if you do have your resources in a package (jar), then you cannot use a path to locate it that uses "..", since there is no "relative path" in a jar archive, it's not actually a file on the filesystem.
Your "resources" are located by the relative path you specify in the getResource... method. A leading "/" means to look at the root of your classpath for locating the resource. No leading "/" means to look relative to the location of the class file that you're using to locate the resource.
If your file is in a location called "com.program.resources", and you're trying to locate it from a class called "com.program.someotherpackage.MyClass", then you'd use:
getClass().getResourceAsStream("/com/program/resources/<file.txt>");
to find it.
Here's my example illustrated:
<classpath root>
com
program
resources
file.txt
img.png
someotherpackage
MyClass.class
Generally, it's common practice to leave resources outside your package structure, to avoid confusion when locating them later. Most IDE's have a way to mark your directories as resources, so when the program is compiled, they will be copied to the proper location in the classpath root, and can be found by any class asking for them.
I have a java application that processes the contents of a file, and then I need to move it to another location.
This is how I read the file:
String filePath = new String("foo.bar");
String fileContents = new String("");
char[] myBuffer = new char[chunkSize];
int bytesRead = 0;
BufferedReader in;
try {
FileReader fr = new FileReader(filePath);
in = new BufferedReader(fr);
try {
while ((bytesRead = in.read(myBuffer,0,chunkSize)) != -1)
{
//System.out.println("Read " + bytesRead + " bytes. They were: " + new String(myBuffer));
fileContents+= new String(myBuffer).substring(0, bytesRead);
}
// close the stream as I don't need it anymore. (If I don't close it, then java would hold the file open thus preventing the subsequent move of the file)
in.close();
fr.close();
} catch (IOException e) {
e.printStackTrace();
return null;
}
} catch (FileNotFoundException e) {
e.printStackTrace();
return null;
}
the file should be closed as I close both input stream and file reader.
Then after this I try to move the file to another directory using File.renameTo(newFileName); but this fails (under unix!, under windows it works fine)
Right after the move fails, I test whether I can create a file called newFileName and whether I can delete the original file. The new file gets to be created, while the original file fails to delete.
Interestingly enough I can delete the original file from command line while the application is running (right after the failure).
Any idea why is that or any alternative?
More details: I am working under unix and I'm bound to use java 1.6 for legacy reasons (thus I can not revert to Files.move() which is supported starting from java 1.7).
I found what was the problem in my java application.
Basically I extract a list of files from a directory using a custom FileFilter. This gives me an array File[] foundFiles.
What I do afterwards is reading each file in a while loop using the snippet of code in the question.
Right after the file is read for some reason I created a new File object using the i-th file from the array as parameter for the constructor
File file = new File(foundFiles[i].getName()); // File to be moved
and then I tried to rename this one.
Now for some reason this works under windows while it doesn't under unix (the file is somehow locked I think by the foundFiles[i] object).
In fact if I print the results of these lines
System.out.println("I can read foundFiles[i]: " +foundFiles[i].canRead());// DEBUG
System.out.println("I can write foundFiles[i]: " +foundFiles[i].canWrite());// DEBUG
System.out.println("I can read file : " +file.canRead());// DEBUG
System.out.println("I can write file : " +file.canWrite());// DEBUG
I get
I can read foundFiles[i]: True
I can write foundFiles[i]: True
I can read file: False
I can write file: False
It was simply enough to use renameTo() directly on the foundFiles[i] objects to make it work fine.
Hope this helps, but I don't know why the first version would work under windows and not under unix.
Let's analyze the above observation...
I can read foundFiles[i]: True
I can write foundFiles[i]: True
I can read file: False
I can write file: False
The result is normal, because the file object has been produced via new File(foundFiles[i].getName()) but the method getName provides only the name of the file, WITHOUT its filepath !
By creating the file via new File(foundFiles[i].getParent() + File.separator + foundFiles[i].getName()), the results would then be :
I can read foundFiles[i]: True
I can write foundFiles[i]: True
I can read file: True
I can write file: True
This is currently what I have to delete the file but it's not working. I thought it may be permission problems or something but it wasn't. The file that I am testing with is empty and exists, so not sure why it doesn't delete it.
UserInput.prompt("Enter name of file to delete");
String name = UserInput.readString();
File file = new File("\\Files\\" + name + ".txt");
file.delete();
Any help would be GREATLY appreciated!
I now have:
File file = new File(catName + ".txt");
String path = file.getCanonicalPath();
File filePath = new File(path);
filePath.delete();
To try and find the correct path at run time so that if the program is transferred to a different computer it will still find the file.
The problem could also be due to any output streams that you have forgotten to close. In my case I was working with the file before the file being deleted. However at one place in the file operations, I had forgotten to close an output stream that I used to write to the file that was attempted to delete later.
Be sure to find out your current working directory, and write your filepath relative to it.
This code:
File here = new File(".");
System.out.println(here.getAbsolutePath());
... will print out that directory.
Also, unrelated to your question, try to use File.separator to remain OS-independent. Backslashes work only on Windows.
I got the same problem! then realized that my directory was not empty. I found the solution in another thread: not able to delete the directory through Java
/**
* Force deletion of directory
* #param path
* #return
*/
static public boolean deleteDirectory(File path) {
if (path.exists()) {
File[] files = path.listFiles();
for (int i = 0; i < files.length; i++) {
if (files[i].isDirectory()) {
deleteDirectory(files[i]);
} else {
files[i].delete();
}
}
}
return (path.delete());
}
Try closing all the FileOutputStream/FileInputStream you've opened earlier in other methods ,then try deleting ,worked like a charm.
I suspect that the problem is that the path is incorrect. Try this:
UserInput.prompt("Enter name of file to delete");
String name = UserInput.readString();
File file = new File("\\Files\\" + name + ".txt");
if (file.exists()) {
file.delete();
} else {
System.err.println(
"I cannot find '" + file + "' ('" + file.getAbsolutePath() + "')");
}
If you want to delete file first close all the connections and streams.
after that delete the file.
In my case it was the close() that was not executing due to unhandled exception.
void method() throws Exception {
FileInputStream fis = new FileInputStream(fileName);
parse(fis);
fis.close();
}
Assume exception is being thrown on the parse(), which is not handled in this method and therefore the file is not closed, down the road, the file is being deleted, and that delete statement fails, and do not delete.
So, instead I had the code like this, then it worked...
try {
parse(fis);
}
catch (Exception ex) {
fis.close();
throw ex;
}
so basic Java, which sometimes we overlook.
As other answers indicate, on Windows you cannot delete a file that is open. However one other thing that can stop a file from being deleted on Windows is if it is is mmap'd to a MappedByteBuffer (or DirectByteBuffer) -- if so, the file cannot be deleted until the byte buffer is garbage collected. There is some relatively safe code for forcibly closing (cleaning) a DirectByteBuffer before it is garbage collected here: https://github.com/classgraph/classgraph/blob/master/src/main/java/nonapi/io/github/classgraph/utils/FileUtils.java#L606 After cleaning the ByteBuffer, you can delete the file. However, make sure you never use the ByteBuffer again after cleaning it, or the JVM will crash.