Question

A comment (by user soc) on an answer to a question about tail call optimisation mentioned that Java 7 has a new feature called “suppressed exceptions”, because of “the addition of ARM” (support for ARM CPUs?).

What is a “suppressed exception” in this context? In other contexts a “suppressed exception” would be an exception that was caught and then ignored (rarely a good idea); this is clearly something different.

Answer 1

I believe the commenter is referring to is an exception which is semi-ignored when it’s thrown within the implicit finally block of a try-with-resources block, in the context of an existing exception being thrown from the try block:

An exception can be thrown from the block of code associated with the try-with-resources statement. In the example writeToFileZipFileContents, an exception can be thrown from the try block, and up to two exceptions can be thrown from the try-with-resources statement when it tries to close the ZipFile and BufferedWriter objects. If an exception is thrown from the try block and one or more exceptions are thrown from the try-with-resources statement, then those exceptions thrown from the try-with-resources statement are suppressed, and the exception thrown by the block is the one that is thrown by the writeToFileZipFileContents method. You can retrieve these suppressed exceptions by calling the Throwable.getSuppressed method from the exception thrown by the try block.

(That’s quoting a section called “Suppressed Exceptions” from the linked page.)