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Is there a way to get the path of a File with "/" instead of "\"?

I am making an HTTP Server in Java so that (on start) it finds all files in a directory (and it's sub-directories) and adds them to the server. But when getting the path of a file and trying to give it to HttpServer.createContext(), it throws a java.lang.IllegalArgumentException: Illegal value for path or protocol. (with the string argument, say "\folder/index.html"). To get this value, I used
file.getParent().substring(24) + "/" + file.getName()
I used substring because I had to exclude the folder the web server is in. The illegal character is the backslash. I have tried extending File to change separator and separatorChar, but that only created 2 new variables. While using String.replace() didn't seem to have any effect. Is there a different method than File.getParent or File.getPath that I can use, or is there a way to use String.replace that I am not seeing?
EDIT:
String.replace() seems to be the best answer... But I am not completely sure how to use it.
EDIT 2: For some reason the backslash isn't showing up, so I changed it.

You have to use the java System.getProperty.
Notice that, in this context, "file.separator" is a key which we are
using to get this property from current system executing the java VM.
Insteady of using a slash (/), you should choose a platform agnostic file separator, as an example it should be:
String separator = System.getProperty("file.separator");
System.out.println(separator);
// unix / , windows \

Have a look at Paths.get(...)
Try Paths.get(".") // current working directory.
Or tell it, on which path it should start:
Use System.getProperty("user.dir"), for current loged in user, home directory.
String pathStr = "/";
Path homeDir = Paths.get(System.getProperty("user.dir"))
Getting from the user directory into the data directory: homeDir.get("data")
Path dataPath = Paths.get(System.getProperty("user.dir"));
File dataFile = dataPath.toFile();
Now use operations on dataFile, to check what files and directories there are, on that location of the file system.

Slash character in file path creating exception in javafx media

I found many similar questions on this topic in this forum, but none of the solutions of those questions working for me and this problem is really making me frustrated.
I have the following method which should play a wav file when I call it.
Directory of the wav file is: ProjectFolder/src/resources/Sounds/click.wav
public static void Click()
{
String clickSound = "/resources/Sounds/click.wav";
Media hit = new Media(new File(clickSound).toPath().toString());
MediaPlayer mediaPlayer = new MediaPlayer(hit);
mediaPlayer.play();
}
But it results in the following exception:
Exception in thread "AWT-EventQueue-0" java.lang.IllegalArgumentException: java.net.URISyntaxException: Illegal character in path at index 0: \resources\Sounds\click.wav
at javafx.scene.media.Media.<init>(Media.java:385)
When I set the value of the string clickSound "resources/Sounds/click.wav" instead of "/resources/Sounds/click.wav", the exception says illegal character in path at index 9.
So I am guessing that it is considering '/' character as an illegal character. I tried using '\' instead of '/', but the result was same.
I do not want to change the location of the wav file for certain reason. How can access I access that wav file from ProjectFolder/src/resources/Sounds/click.wav and play it without any exception?
Any kind of help is appreciated.
Thanks in advance.

As stated in the documentation:
The source must represent a valid URI and is immutable. Only HTTP, HTTPS, FILE, and JAR URLs are supported. If the provided URL is invalid then an exception will be thrown.
You are passing in the path to a file, instead of a URI.
You almost certainly don't want a file here anyway; for example, when you deploy your application it will typically be deployed as a jar file, and the media will be an entry in that jar file (so it won't be a file in its own right at all). On top of that, the resources folder is typically part of the source code structure, and for obvious reasons the source code is not usually available at runtime.
Assuming your resources are being deployed to the root of the classpath, which is the usual setup, you need something like
String clickSound = "/Sounds/click.wav";
Media hit = new Media(getClass().getResource(clickSound).toExternalForm());

You listed the file as in directory "ProjectFolder/src/resource/Sounds/click.wav" but when trying to access you have "resources" instead of "resource"

Launching a text file from a .jar file (File path?)

I'm trying to launch a text file from a .jar file using Desktop.getDesktop().open(file)
String fileName = "file.txt";
URL url = getClass().getResource(fileName);
File fileToRead = new File(url.toURI());
Desktop.getDesktop().open(fileToRead);
I omitted the try-catch blocks for simplicity.
It is able to open my file when run from eclipse. But once I export to a .jar file, I get a NullPointerException in File fileToRead = new File(url.toURI());

When you package a class in a .jar file, it usually makes it nested one level deeper.
Therefore, you can try changing the first line to:
String filename = "../file.txt";

Looking at the JavaDoc of Class.getResource(String):
an absolute resource name is constructed from the given resource name using this algorithm:
If the name begins with a '/', then the absolute name of the resource is the portion of the name following the '/'.
Otherwise, the absolute name is of the following form:
modified_package_name/name
Where the modified_package_name is the package name of this object with '/' substituted for '.'.
Parameters:
name - name of the desired resource
Returns:
A URL object or null if no resource with this name is found
Your resource was not found, hence NullPointerException. Specify the path within the JAR as described by the JavaDoc (absolute path starting with '/' or relative to the class of this, the object where you are calling getClass().getResource(fileName)) and you should get it.

How to get to a file by passing relative path in java?

I am trying to understand "How to get to file by passing relative path of a file or folder?" . Here is the example:
CODE:
public class somex {
public static void main {
String fileName = System.getProperty("user.dir"); <---This gives me path for the current working directory.
File file = new File(fileName + "../../xml_tutorial/sample.xlsx" );
System.out.println(file.getCanonicalPath()); <---This gives me path for the file that is residing in folder called "xml_tutorial".
}
}
>>>>
Here, I know the file location so i was able to pass correct relative path. And, managed to print the file path. I have deleted the "sample.xlsx" and executed the above code; With no failing it gives me the path name and it is same path as when the file exists (i.e. before deleting). How it is possible ? I am expecting EXCEPTION here. why it is not throwing exception ?
Two, I want to use regular expression for the file name, such as: "../../xml_tutorial/samp.*". But this doesn't do the job and it gives me IOException. Why it is not able to identify the file sample.xlsx ? (NOTE: this is when the file exist and one hundred precent sure there is only one file with the name "sample.xlsx")

I have deleted the "sample.xlsx" and executed the above code; With no failing it gives me the path name and it is same path as when the file exists (i.e. before deleting). How it is possible ? I am expecting EXCEPTION here. why it is not throwing exception ?
File doesn't care whether the file actually exists. It just resolves the path. There's no need for the file to exist in order to take the path
/home/tjc/a/b/c/../../file.txt
...and turn it into the canonical form
/home/tjc/a/file.txt
If you want to know whether the file on that path actually exists, you can use the exists() method.
On your second, unrelated question:
Two, I want to use regular expression for the file name, such as: "../../xml_tutorial/samp.*". But this doesn't do the job and it gives me IOException. Why it is not able to identify the file sample.xlsx ?
There's nothing in the File documentation saying that it supports wildcards. If you want to do searches, you'll want to use list(FilenameFilter) or listFiles(FilenameFilter) and a FilenameFilter implementation, or listFiles(FileFilter) and a FileFilter implementation.

java.net.URISyntaxException

I have get this exception. but this exception is not reproduced again. I want to get the cause of this
Exception Caught while Checking tag in XMLjava.net.URISyntaxException:
Illegal character in opaque part at index 2:
C:\Documents and Settings\All Users\.SF\config\sd.xml
stacktrace net.sf.saxon.trans.XPathException.
Why this exception occured. How to deal with so it will not reproduce.

A valid URI does not contain backslashes, and if it contains a : then the characters before the first : must be a "protocol".
Basically "C:\Documents and Settings\All Users\.SF\config\sd.xml" is a pathname, and not a valid URI.
If you want to turn a pathname into a "file:" URI, then do the following:
File f = new File("C:\Documents and Settings\All Users\.SF\config\sd.xml");
URI u = f.toURI();
This is the simplest, and most reliable and portable way to turn a pathname into a valid URI in Java. It should work on Windows, Mac, Linux and any other platform that supports Java. (Other solutions that involve using string bashing on a pathname are not portable.)
But you need to realize that "file:" URIs have a number of caveats, as described in the javadocs for the File.toURI() method. For example, a "file:" URI created on one machine usually denotes a different resource (or no resource at all) on another machine.

The root cause for this is file path contains the forward slashes instead of backward slashes in windows.
Try like this to resolve the problem:
"file:" + string.replace("\\", "/");

You must have the string like so:
String windowsPath = file:/C:/Users/sizu/myFile.txt;
URI uri = new URI(windowsPath);
File file = new File(uri);
Usually, people do something like this:
String windowsPath = file:C:/Users/sizu/myFile.txt;
URI uri = new URI(windowsPath);
File file = new File(uri);
or something like this:
String windowsPath = file:C:\Users\sizu\myFile.txt;
URI uri = new URI(windowsPath);
File file = new File(uri);

It needs a complete uri with type/protocol
e.g
file:/C:/Users/Sumit/Desktop/s%20folder/SAMPLETEXT.txt
File file = new File("C:/Users/Sumit/Desktop/s folder/SAMPLETEXT.txt");
file.toURI();//This will return the same string for you.
I will rather use direct string to avoid creating extra file object.

I had the same "opaque" error while passing a URI on the command line to a script. This was on windows. I had to use forward slashes, NOT backslashes. This resolved it for me.

it doesn't like spaces as well and it has to be / instead of \ or `\ or //
zipFilePath = "C:/test/v";