Exception Handling

Question 1

What is an exception?

Answer 1

run-time error

an abnormal condition that arises at runtime.

Question 2

How does exception handling work?

Use the words try, catch, throw, finally

Answer 2

Use a try block to monitor for exceptions.
If exception occurs, it is thrown.
The code can catch the exception and handle it in some way.
finally specifies code that will run after the try block

Question 3

How do you define the exception to the thrown from a method?

Answer 3

throws

static void throwOne() throws IllegalAccessException {
throw new IllegalAccessException(“demo”)

Question 4

What is the superclass of all exceptions?

Answer 4

Throwable

Question 5

What are the two subclasses of Throwable?

Answer 5

Exception - normal, in user programs, used to create own exceptions

Error - catastrophic, usually having to do with runtime environment

Question 6

T/F: once an exception is thrown, it must be caught.

Answer 6

True.

If not specified, default handler will handle it

Question 7

Do you need to include catch in a try statement?

Answer 7

no

Question 8

Whats the goal of a catch clause?

Answer 8

resolve the error condition then continue on as if the error never occured.

in contrast to without it, the program would stop.

Question 9

Can you have multiple catch clauses?

Answer 9

yes. The execute in order, then stop when one is hit.

Question 10

For multiple catch clauses, Why do exception subclasses must come before their superclass?

Answer 10

Because it’ll produce an “unreachable code” error in that the exception will never be able to get to the subclass because it’ll always be caught with the superclass before

Question 11

what is “throw” used for?

Answer 11

Can determine the exception to throw instead of the default provided by java

Question 12

Why does a method need to define the exceptions it can throw?

Answer 12

so that the method caller can handle it.

Only need define the ones outside of type Error or RuntimeException which are included in java

Question 13

Will a finally block execute even if an exception is not found?

Answer 13

yes

Question 14

T/F

think of try, throw, and catch as clean ways to handle errors and unusual boundary conditions in your program’s logic

Answer 14

ya

Question 15

in Exception class, what method do you call to get the description of the error?

Answer 15

except.getMessage()

Question 16

in Exception class, what method do you call to get the flow of where the error came from?

Answer 16

except.printStackTrace()

Question 17

What is Java exception hierarchy of classes

Answer 17