Helper to call close() if implements AutoCloseable?

Question

Is there any helper method in the JDK or common libraries that does this:

if (resource instanceof AutoCloseable) {
    ((AutoCloseable) resource).close();
}

Just a one-liner to call an object's close() if applicable.

I know about try-with-resources, that's not applicable to this situation. And I know that not all classes that have a close() method implement AutoCloseable. But, I seem to write the above over and over..

That looks like a XY problem. Can you tell more about the context? You should not have to use `instanceof`. — fge, Mar 23 '14 at 20:07
fge: yes a clarification is in order: I have a ref to an interface, at compile time I can't know if the impl also implements AutoCloseable in addition to the interface. — tariksbl, Mar 23 '14 at 20:38
That would restrict to AutoCloseable impls; I'm looking to ".. call an object's close() *if applicable* ". — tariksbl, Mar 23 '14 at 20:53
That really doesn't look right at all. There is something fundamentally wrong with this approach, you should explain your problem more. — fge, Mar 23 '14 at 20:56
I don't get it. You shouldn't have code that closes resources it didn't allocate. Resource-allocating code should use an ARM block. — erickson, Mar 23 '14 at 21:41

score 0 · Answer 1 · answered Mar 23 '14 at 20:06

0

There's something Apache Commons offers:

http://commons.apache.org/proper/commons-io/apidocs/org/apache/commons/io/IOUtils.html#closeQuietly(java.io.Closeable)

answered Mar 23 '14 at 20:06

Haris Osmanagić

1,249
12
28

4

Doesn't help. For one, there is no requirement that an `AutoCloseable` also implements `Closeable`. And second, this utility pales in comparison to Guava's `Closer`. – fge Mar 23 '14 at 20:08

score 0 · Answer 2 · answered Nov 20 '17 at 19:35

Here is apache commons closeQuietly adapted for AutoCloseable:

  static void closeQuietly(AutoCloseable closeable) {
    try {
      if (closeable != null) {
        closeable.close();
      }
    }
    catch (Exception swallowed) {
    }
  }

since google sent me here for that case :)

Marco Acierno · Answer 3 · 2014-03-23T20:37:30.510

-1

Edit:

Check this:

class CloserHelper
{
    public static void close(Object object)
    {
        if (object instanceof AutoCloseable)
        {
            try
            {
                ((AutoCloseable) object).close();
            }
            catch (Exception ignored) { }
        }
    }
}

I can think to something like this

class CloserHelper
{
    public static void close(AutoCloseable obj) throws Exception
    {
        obj.close();
    }
}

Then

CloserHelper.close(resource);

If the object is not a AutoCloseable you cannot just call it

If you want to ignore exceptions

class CloserHelper
{
    public static void close(AutoCloseable obj)
    {
        try
        {
            obj.close();
        }
        catch (Exception e) { }
    }
}

edited Mar 23 '14 at 20:37

answered Mar 23 '14 at 20:04

Marco Acierno

14,682
8
43
53

Marco: I have a ref to an interface, at compile time I can't know if the impl also implements AutoCloseable in addition to the interface. – tariksbl Mar 23 '14 at 20:22
`catch (Exception e)` <-- bad. You also catch all unchecked exceptions with that. And that includes `NullPointerEception`. – fge Mar 23 '14 at 20:43
@fge Yes, my code want to ignore all exceptions. Anyway instanceof will avoid null so no NullPointerException – Marco Acierno Mar 23 '14 at 20:44

Helper to call close() if implements AutoCloseable?

3 Answers3