Question

Has anyone ever seen an exception thrown when calling close method on any closable object?

Answer 1

An IOException will be thrown on close if the final flush fails. Possible causes include:

• the file system is full, or the user is over quota,
• hard disc errors,
• a file system was forcibly unmounted,
• a remote file system is unavailable due to networking or other problems,
• (possibly) a character encoding error if writing to the file via an OutputStreamWriter or similar,
• a device error if the “file” is a device file,
• a lost connection if the closeable is a network stream,
• a broken pipe if the closeable is a pipe to external process,
• and so on.

I have certainly seen some of these. Others are unlikely.

However, if the data you are writing is important then you should allow for close failing. For example, if your application is writing out a critical file the file system fills up, your application had better notice this before it replaces the old copy of the file with the truncated version.