mode 6

Question 1

What is an exception?

Answer 1

An exception is an exceptional event (aka an issue) that arises INSIDE of your program’s logic. More than likely the programming logic is fault or dangerous or careless.

Question 2

What is….an error?

Answer 2

An exception is an exceptional event (aka an issue) that arises OUTSIDE of your program’s logic. More than likely the issue with with your runtime environment or system.
>examples:
>StackOverflowError
>OutOfMemoryError

Question 3

What is the hierarchy of exception handling in java?

Answer 3

(Throwable 	[class])
						|
					  /			\
					/			  \
		(Exception	[class])		(Error	[class])
			|
		(RuntimeException [class])

Question 4

Keywords associated with exception handling in java?

Answer 4

• try, catch, finally
• throw
• throws

Question 5

What is a “checked” exception?

Answer 5

The compiler will give you a syntax error if you do NOT “handle” the logic that could potentially throw an exception/error.

In short, when you do NOT handle an exception it will lead to a syntactical error, the syntax error itself is NOT the exception being thrown.
example:
FileNotFoundException
IOException

Question 6

What is an “unchecked” exception?

Answer 6

The compiler will NOT force you to “handle” the logic that could potentially throw and exception/error. meaning there will be no syntax error created.

Note: if you EVER see an unchecked exception YOU need to refactor your code, because you as the developer have made a mistake or was careless
example:
IndexOutOfBoundsException
InputMismatchException

Question 7

How do we handle a checked exception

Answer 7

A try-catch block is how we handle a checked exception.

Question 8

Can we have multiple catch blocks?

Answer 8

Yes, just make sure that specific exceptions go before general exceptions. The order matters.

Question 9

What is the purpose of a try block?

Answer 9

The purpose of a try block is to attempt volatile code. You “try” the volatile code and if the volatile code behaves poorly then you have a “catch” block with some fallback, less volatile, code.

Question 10

can we catch a RuntimeException?

Answer 10

Yes

Question 11

CAN I THROW AN ERROR? AND CAN I CATCH AN ERROR?

Answer 11

Yes, but there’s no need to since the Error only informs about the existence of the error but there’s no way for us to do anything meaningful about it

Question 12

Aside from try-catch, is there another way to handle exceptions in Java?

Answer 12

Yes, using the throws keyword

We can use the “throws” keyword…aka a concept called “ducking”
It’s called “ducking” because we’re ducking responsibility

When we use the “throws” keyword, the invoking method now has to “handle” the exception, we no longer need to.

Question 13

What is the finally block?

Answer 13

The objective of the finally block is to run its logic regardless of whether or not there is an exception thrown.

The finally is often used as a place to put clean up logic, like cleaning up memory, closing streams, etc.

Question 14

Understanding a stacktrace

Answer 14

Format of the stack trace:

Exception in [thread] [package].[class] : [additional message]
at [package1].[method1] ([file-name1] : [line number] )

Question 15

When was finalize() method used?

Answer 15

We USED to use the finalize() method, which is called while the garbage collector is disposing of your objects. But now, we just use the finally block

Question 16

Will the finally block ALWAYS run?

Answer 16

TECHNICALLY there are cases where the finally block won’t run:

• 1. System.exit();
• 2. System failure/fatal error

Question 17

What are the dos and don’ts of try-catch block

Answer 17

We MAY have:

• a try-catch block
• a try-finally block (as long as the try doesn’t contain a checked Exception)
• a try-catch-finally

We may NOT have:
-a try block by itself

Question 18

What is a lambda?

Answer 18

a lambdas is essentially a disembodied function….

Question 19

How are lambda expressions formed?

Answer 19

Lambda expressions create an instance of a functional interface on the fly, using an anonymous method implementation.

Question 20

LAMBDA FORMAT:

Answer 20

FunctionalInterface myInter =	(parameter-list) ->  {
		 						//logic				};

Question 21

Use cases for lambdas?

Answer 21

comparable, comparator, runnable, etc.