Question

Possible Duplicate:
JDK 1.7 Throwable `addSuppressed()` method

So Java has a method in the Throwable

public final void addSuppressed(Throwable exception) 

And this is what it does:

Appends the specified exception to the exceptions that were suppressed
in order to deliver this exception. This method is thread-safe and
typically called (automatically and implicitly) by the
try-with-resources statement.

..i’m puzzled at this , what is “specified exception to the exceptions that were suppressed
in order to deliver this exception.” ?

Answer 1

There is a pretty good explanation in the docs: Throwable

The suppression behavior is enabled unless disabled via a constructor.
When suppression is disabled, this method does nothing other than to
validate its argument.

Note that when one exception causes another exception, the first
exception is usually caught and then the second exception is thrown in
response. In other words, there is a causal connection between the two
exceptions. In contrast, there are situations where two independent
exceptions can be thrown in sibling code blocks, in particular in the
try block of a try-with-resources statement and the compiler-generated
finally block which closes the resource. In these situations, only one
of the thrown exceptions can be propagated. In the try-with-resources
statement, when there are two such exceptions, the exception
originating from the try block is propagated and the exception from
the finally block is added to the list of exceptions suppressed by the
exception from the try block. As an exception unwinds the stack, it
can accumulate multiple suppressed exceptions.

An exception may have suppressed exceptions while also being caused by
another exception. Whether or not an exception has a cause is
semantically known at the time of its creation, unlike whether or not
an exception will suppress other exceptions which is typically only
determined after an exception is thrown.

Note that programmer written code is also able to take advantage of
calling this method in situations where there are multiple sibling
exceptions and only one can be propagated.