read from a file that is in the same folder as the .jar file

Question

Is there a way to read from a file that is in the same folder as the .jar file? I am trying to create a java program that has to read from a file when I turn in my assignment. I do not know where the file or program will be held once I turn it over so I dont think I can encode the directory of the held file. Is this possible? The problem is that i have to upload the file to a CSX hosts server which is a linux server and run it from there. If I dont put a path before the file will it just search its current folder location?

Answer 1

You can get the location of the JAR file containing any specific class via:

URL url = thisClass.getProtectionDomain().getCodeSource().getLocation();

From there it is easy to relativize a URL to the desired file.

Answer 2

As noted in the comments, this works only if you run the command from the directory the jar is in.

(In the context of a desktop application)
To access a file that's in the current directory of the jar, your path to the file should be preceded by a dot. Example:

String path = "./properties.txt";
FileInputStream fis = new FileInputStream(path);
BufferedReader in = new BufferedReader(new InputStreamReader(fis));
// Read the file contents...

In this example, there is a text file called properties.txt in the same directory as the jar.
This file will be read by the program contained in the jar.

Edit: you said the filename would not change, and this answer applies given that you know the name beforehand, of course, should you prefer to hardcode it.