Question

The problem: I need to ensure that a particular directory hierarchy exists in the file system, and create it if it doesn’t.

I know that there is the method File.mkdirs() however the javadocs for that method indicate that it could fail creating some or all of the directories necessary to complete the path given.

To get around that, I made a method that takes a String representing the path and parses it into the individual parts, storing them into an ArrayList<String>. A second method would then go through and build the directories up, making sure that each directory and sub directory existed.

The problem is, the actual program runs out of memory when trying to loop through and break up the string into its individual parts. I know it’s not the function; it works perfectly on its own in a JUnit test, and the program itself isn’t very memory intensive. At this point, it’s just set directories up and stored them into a “DataBank” class – nothing big, just a class storing a bunch of strings.

I’d like to figure out what’s causing the problem; I can reply with the different classes in effect at the point the code stops.

However, a simpler solution might just be to use File.mkdirs(). What would cause File.mkdirs() to not create directories? Would it just be insufficient permissions?

I’d like to simplify the process if I can, instead of trying to re-invent the wheel. At the same time, though, I know that the program should not be running out of memory – I’m storing Strings and performing file operations, nothing super intensive.

Answer 1

However, a simpler solution might just be to use File.mkdirs(). What would cause File.mkdirs() to not create directories? Would it just be insufficient permissions?

File.mkdirs() could fail for any of the reasons that File.mkdir() fails (except for failing due to the parent directory not existing (for obvious reasons)).

From the Javadoc:

public boolean mkdirs()

Creates the directory named by this abstract pathname, including any necessary but nonexistent parent directories. Note that if this operation fails it may have succeeded in creating some of the necessary parent directories

The bold bit is a clue that mkdirs() is just a shortcut for multiple calls to mkdir().

Here’s what mkdirs() does – it effectively calls mkdir() up the directory hierarchy:

public boolean mkdirs() {
    if (exists()) {
        return false;
    }
    if (mkdir()) {
        return true;
    }
    File canonFile = null;
    try {
        canonFile = getCanonicalFile();
    } catch (IOException e) {
        return false;
    }

    File parent = canonFile.getParentFile();
    return (parent != null && (parent.mkdirs() || parent.exists()) &&
            canonFile.mkdir());
}