Simple question about File class in kotlin-CodePudding

I'm trying to read from a file in kotlin using the File class. It's just a simple txt file with a list of names with each name occupying an independent row. This is my project structure:

and here's my function for pulling out a name depending on the day of the year:

private fun getNameOfTheDay(): String {
        val cal = Calendar.getInstance()
        val day = cal[Calendar.DATE]

        return File("data${File.separator}names.txt")
            .bufferedReader()
            .lineSequence()
            .elementAt(day - 1)
    }

I keep on getting a FileNotFound exception so I would assume that my file path is somehow wrong... What am I doing wrong here? Sorry for the dumb question, I'm still learning. By the way the function shown above is called from the MainActivity. Thanks in Advance!

CodePudding user response：

You should try "data\names.txt". Oftentimes slashes don't work for file paths.

CodePudding user response：

Filenames can be absolute or relative. Absolute filenames start from the top level (e.g. the root directory on Unix-like filesystems, which Macs have; or a drive letter on Windows), and so specify the filename unambiguously. Relative filenames don't, and so give a file in (or in relation to) the current working directory.

In this case, data/names.txt is a relative filename. It assumes that the current directory has a subdirectory called data, and refers to a file in that.

However, the file is actually in the directory app/src/main/java/com/example/mynameis/data/ within your project — so this would only work if the current directory was /<pathToYourProject/app/src/main/java/com/example/mynameis/, which is highly unlikely! So that probably explains the failure.

I don't know about Android projects, but in normal JVM projects the standard practice is to put data files in a src/main/resources/ directory. Gradle (or Maven) knows to copy them into the classpath when building the project. You would then load it from the classpath, e.g. with:

javaClass.getResource("data/names.txt").readText()

See e.g. this question for more details and variations.

The advantage of loading from the classpath instead of a file is that you don't need to know exactly where the file is; it could be loose on the filesystem, or bundled into a jar or other archive (even compressed), with ways to select between different versions depending on the run profile — all completely transparent to your code.

As I said, I don't know Android, and can't find any direct answers on StackOverflow. (This question seems to suggest using a android.resource:// URI, but I don't know if that would apply here.) Maybe these external sites can give you some hints.