File.mkdir不会抛出IOException但File.createNewFile会抛出IOException

Question

The File class lets you create new directories and new files on a file system.

The methods to accomplish this are:

public boolean createNewFile() throws IOException
-and-
public boolean mkdir()

How does the operation of creating a new file potentially lead to an IOException being thrown but the operation of creating a new directory does not?

I'm trained as a Java developer to be very aware of operations that throw checked exceptions, so I would be expecting more consistency here unless there was a very good reason for the lack of consistency. Both methods return true if the operation succeeded.

Answer 1

Because it's part of the API :

 public boolean mkdir() 

Creates the directory named by this abstract pathname.

Returns:
true if and only if the directory was created; false otherwise

I would accept that the API could be improved in this respect.

Answer 2

We can only guess, but my guess is that the main reason is that they learned.

createNewFile() was added in Java 1.2, which is several years after Java 1.0. And they have since learned that using return values are a bad way to communicate error conditions (they knew it before, but didn't apply it everywhere).

Note that when createNewFile() exists without an exception, then the requested file exists! The only distinction made by the return value is whether or not it existed before.

If it fails to create the file, then an exception is thrown.