10.1 Understanding Exceptions

Question 1

📝️ What is a Java Exception?

Answer 1

An exception is an event that disrupts/alter the normal flow of an application

Question 2

📝️ What is the java.lang.Throwable class?

Answer 2

It’s the Java superclass for all objects that represent an Exception event.

Question 3

📝️ What are the key subclasses of Throwable

(Exception-types)?

Answer 3

• > Error
• > RuntimeExceptions [Unchecked]
• > Exceptions [Checked Exceptions]

Question 4

📝️What does the 💥️Error💥️ class represents (examples)?

Answer 4

• > An Error means something went so horribly wrong that your program should not attempt to recover from it.
  e. g: The disk drive “disappeared” or the program ran out of memory.

Question 5

📝️ What does 💥️Checked Exception💥️ mean in Java?

Answer 5

• > Checked exceptions include any class that inherits Throwable, but does NOT inherit from Error nor RuntimeException classes.
• > It’s an exception that needs to be anticipated in other words, it must be caught or declared.

Question 6

📝️ What is an 💥️Unchecked Exception💥️ class?

Answer 6

o An Unchecked exception is a RuntimeException or any of its subclasses.
o It does NOT have to be handled nor declared.
o This kind of exceptions can be thrown by the JVM itself or the programmer code.

Question 7

What Exception classes…

are Catcheable or Have to be Declared (Table)?

Answer 7

👉️ Error |✅|✅| ⚠️ You shouldn’t but you can
👉️ Unchecked Exc. |✅|✅| ❓️ You can but you don’t have to
👉️ Checked Excep |✅|✅| 💪️You have to

Question 8

📝️ What does the 💥️HANDLE OR DECLARE💥️ rule means?

Answer 8

It means that Checked Exceptions should be handle or declared
👉️ handle -> 🕵‍♂️️’throw’ Wrapped in compatible try and catch blocks
👉️ declared -> 🕵‍♂️️’throws’ Defined that this method ‘throws’ a certain exception in the method signature …(someone else will handle it.)

Question 9

📝️ What are the keywords used to declare and delegate exception handling (when)?

Answer 9

• > throw - When a particular condition is matched we can throw an Exception …e.g: throw new IOException();
• > throws - It is used at the end of a method declaration …e.g: throws IOException

Question 10

📝️ What is the ‘throw’ keyword used for?

Answer 10

o It’s used to declare a new exception (throw) or re-throw an existing one.
-> It goes as an statement inside a code block.

Question 11

📝️ What does throws statement mean in java?

Answer 11

-> The throws keyword indicates that a certain method can potentially “throw” an specific exception.