如果系统抛出已检查的异常，是否可以被默认处理程序捕获？

Question

Also, does the default handler catches an exception thrown by us? If yes, then does it depend on whether the exception is checked or not?

Answer 1

Any Throwable can be caught. But subclasses of Error are not intended to be caught by user application code. They still can be caught, but some errors may even leave application in bad state ( OutOfMemoryError for example).

Answer 2

A catch block will catch any sub-type of the declared Throwable type. For example catch (Exception ex) {} will handle any Exception that is thrown in the try block, as even RuntimeException (un-checked) is a child.

Note that this will not catch instances of Error, since they are not a sub-class of exception. If you really want a catch all, you can use something like catch (Throwable th) . This is not advisable, since Error's, are usually an indication of a problem that the application cannot easily recover from by itself.

Answer 3

There's a little-known fact about checked/unchecked exceptions: The distinction exists only at compile time.

If, by some ugly trick, you manage to throw a checked exception at a place where it isn't declared to be thrown, then it will be handled just like an unchecked exception (ie it will will fall through as many stack frames as necessary to reach the nearest matching catch block). And yes, such tricks exist.

And if by default handle your mean the Thread default uncaught exception handler (or the per-thread uncaught exception handler ), then yes: they will handle both checked and unchecked exceptions that are not handled by catching them "normally".