Writing to a resource inside the JAR, URI not hierarchical?

[Josh Bern]

Hi people, I'm new and this forum seems active!
I'm using NetBeans IDE and my directory structure looks like this:


I tried writing to a text file in the jar, can you folks see what's causing the exception in the command prompt when the following class is run in console like: java -jar "mypath/myjar.jar"? Thanks!

//class MyMain

//Declaring fields
public static final String MY_FILE = "res/myfile.txt";
//A filename of a text file in the "res" folder is a static field.

//Entering main() to read in file and process
InputStream s = MyMain.class.getClassLoader().getResourceAsStream(MY_FILE);
//For reading the text file, so far so good, 
//it reads the txt from the res folder inside the jar when run from console.

//Processing done, now I want to write to MY_FILE
PrintStream ps = new PrintStream(new File(MyMain.class.getResource(MY_FILE).toURI()));
//Tried this for opening the text resource in the jar, but at this line
// the following exception is thrown when run from console (compiles ok)

Exception in thread "main" java.lang.IllegalArgumentException: URI is not hierarchical

[Wouter Oet]

You can't write data into an existing jar file to my knowledge. You can however write it to a plain file and then make it a jar (zip) file.

[Wouter Oet]

And welcome to the JavaRanch.

[Josh Bern]

Yo Wouter Out, thanks. Ok say I want to store simple text data inbetween runs, is my best option to store a text file in the same directory as the JAR? I'd love to bake it in somehow, but it's not worth it if it's too complicated.

[Wouter Oet]

Yea that is probably the easiest solution.

Btw it's Wouter Oet but please just call me Wouter.

[Josh Bern]

I'm unsure how to make the text file appear in the dist folder besides the jar and how to write to it when the jar is run. I changed the path to this:

public static final String MY_FILE = "myfile.txt";

...and draged the text file to the dist folder by the jar. I type this in the command prompt:

C:\Documents and Settings\myName>java -jar "C:\Documents and Settings\myName\My Do
cuments\NetBeansProjects\myProject\dist\myjar.jar"


//When about to read in the file, not writing yet, this error materializes:
Exception in thread "main" java.lang.NullPointerException
at java.io.Reader.<init>(Unknown Source)
at java.io.InputStreamReader.<init>(Unknown Source)
at java.util.Scanner.<init>(Unknown Source)
at MyMain.main(QuestionMain.java:27)