enum

Question 1

What is an enum?

Answer 1

It's short for “enumeration/enumerated type” 
 -> Is like a fixed set of constant values.
 -> It can be a top‐level/nested-type.
🤯️⚠️📣️ Behind the scenes, an enum is a type of class that mainly contains static members
🤓️ Enum values are commonly written using Upper Snake Case -> OCKY_ROAD,MINT_CHOCOLATE_CHIP...

Question 2

What about enum composition?

Answer 2

🤯️⚠️📣️ Enums can have more in them than just a list of values (members/constructors/methods*)
* including… static void main(String args[])

Question 3

What about enum syntax?

Answer 3

🤯️⚠️📣️ The compiler requires the list of values must be always declared at first.
🤯️⚠️📣️ Semicolon is optional if enum is just composed of a list of values -> Otherwise it’s MANDATORY 👀️😬️

Question 4

📝️ What are the most common enum helper methods (5)?

Answer 4

name()|values()|ordinal()|toString()|valueOf()

Question 5

🕵‍♂️️🤓️🔎️ What is the Difference between name() and toString() ?

Answer 5

-> The main difference between name() and toString() is that name() is a final method, so it cannot be overridden. The toString() method returns the same value that name() does by default, but toString() can be overridden by subclasses of Enum to return a more user-friendly name.

Question 6

What does the valueOf() method do?

Answer 6

🤯️⚠️📣️ The valueOf() method allow us to retrieve an enum value from a String.
-> If there is no enum constant for that value, it’ll throw ⚠️❌IllegalArgumentException❌⚠️

Question 7

What about enum comparisson?

Answer 7

🤯️⚠️📣️ An enum is like any other type so when compared against other type compiler will complain:
❌ Season.WINTER == “WINTER” //Won’t compile (incomparable type)
⚠️ Season.WINTER.equals(“WINTER”) //false

Question 8

How to use an ENUM in a SWITCH statement?

Answer 8

🤯️⚠️📣️ When using enums in switch statement the case branchesHow to use an ENUM in a SWITCH statement? only allow enum-value(s) -> 💥️name()

Question 9

📝️ What about enum and access-modifiers?

Answer 9

-> An enum is implicitly public. Can’t be marked as ❌protected or ❌private

Question 10

📝️ Can an enum be extended?

Answer 10

An enum can NOT be extended

-> public enum Extended

Question 11

🛸️ How to Add Constructors, Fields, and Methods?

Answer 11

🤯️⚠️📣️ enum-value(s) may define a body where we can…

• > ✅ Invoke methods and constructor’s (curly braces are not mandatory)
• > ❌ member-fields can NOT be declared there (✅This can be done outside of it)

        enum Season {
	    WINTER("winter"),
	    SUMMER("summer"),
	    SPRING() {
		this.value = "sprIng"; //❌
	}

Question 12

📝️ How do we call an enum field/method?

Answer 12

• > Season.SUMMER.fieldName;

- > Season.SUMMER.methodName();

Question 13

What about enum constructors?

Answer 13

🤓️ enum constructors are implicitly private, with the modifier being optional.
🕵‍♂️️👓️ This is reasonable since you can’t extend an enum
🕵‍♂️️👓️ The constructors can be called only within the enum itself
🧠️ An enum constructor will not compile if it contains a 💥️public💥️ or 💥️protected💥️ modifier.