How to see if resource file exists in Java?

Question

I am trying to output text to a resource file in Java like so:

File file = new File(MLM.class.getClassLoader().getResource("mazes.txt").toString());
BufferedWriter out = new BufferedWriter(new FileWriter(file));
..

but because the resource file has not been created I get a null pointer exception. How can I create a blank resource file first if it doesn't exist already to avoid this error?

Please check this post: http://stackoverflow.com/questions/1816673/how-do-i-check-if-a-file-exists-java-on-windows — adis, Feb 21 '12 at 16:00

Johan Sjöberg · Answer 1 · 2017-10-24T16:14:41.553

59

A simple null check would suffice

URL u = MLM.class.getResource("/mazes.txt");
if (u != null) {
         ...
}

From the javadoc for getResource

Returns:
A URL object or null if no resource with this name is found

edited Oct 24 '17 at 16:14

answered Feb 21 '12 at 16:00

Johan Sjöberg

47,929
21
130
148

3

Didn't work for me, but MLM.class.getResource("mazes.txt") worked. – Anthony Apr 16 '16 at 13:04
I need an absolute path, like this `MLM.class.getResource("/mazes.txt")` – akop Oct 23 '17 at 08:29
Worked for me : URL resource = MyClassWithMainMethod.class.getResource("/myfile.xml"); – granadaCoder Mar 01 '19 at 15:58

score 0 · Answer 2 · answered Feb 21 '12 at 16:00

You can use before your code :

File.createNewFile()

Atomically creates a new, empty file named by this abstract pathname if and only if a file with this name does not yet exist. The check for the existence of the file and the creation of the file if it does not exist are a single operation that is atomic with respect to all other filesystem activities that might affect the file.

How to see if resource file exists in Java?

2 Answers2