Hacker News new | ask | show | jobs
by hombre_fatal 2403 days ago 

    OutputStream out = new BarOutputStream();
    in.transferTo(out);
    if (out != null) ...
Can someone explain how `out` could possibly be null here?
2 comments
jay-anderson 2403 days ago
How it's written here it won't be null. However the general pattern is to check for null in the finally block since it may not be provable that the stream is non-null (e.g. created in a library call or similar). In fact the try-with-resources feature handles the null case as well.
link
kitd 2403 days ago
In the article, the if check occurs in a finally clause. So the code would execute even if the constructor threw an exception. Hence the need to null-check it first.
link
hombre_fatal 2403 days ago
But that just isn't true. Neither finally-block appends a try-block that initializes the stream that it null-checks.

If the `in` stream init throws, the entire try-block isn't run at all. If `out` stream init throws, the following try/finally block isn't run either.

Lombok's docs get this wrong too. Unless I'm going crazy.

link