ENUMERATIONS AND NESTED CLASSES

🧠 ENUMERATIONS AND NESTED CLASSES (Mini Study Guide)

🔹 1. ENUMERATIONS (ENUM)

📌 What is an Enum?

An enumeration (enum) is a data type with a fixed set of constants.
👉 Meaning: limited lang ang possible values — hindi pwedeng kung ano-ano.

💡 This part is important kasi ito ‘yung foundation ng topic.

🔍 Example:

public enum Period {
 PRELIM, MIDTERM, PREFINAL, FINAL;
}

🧠 Real-Life Analogy:

Days of the week → Monday to Sunday lang (walang “Funday” ❌)
Traffic light → RED, YELLOW, GREEN lang

❗ Why Use Enum?

Without Enum 😬	With Enum 😎
Possible invalid values (e.g., "MIDTRM")	Strict values only
Errors appear at runtime	Errors caught at compile time
Less safe	Type-safe

👉 In short: Enums = SAFE + ORGANIZED

🧪 Declaring & Using Enum

Period p;
p = Period.MIDTERM;

👉 Think of it like:

“p can ONLY be one of the official periods.”

🔹 2. ENUM METHODS (Built-in)

Enums are actually classes, so may built-in methods sila 🤯

📊 Important Methods:

Method	What it does	Example
`toString()`	Returns name	"MIDTERM"
`ordinal()`	Position (starts at 0)	MIDTERM = 1
`equals()`	Checks equality	false if different
`compareTo()`	Compares order	positive/negative/0

🧠 Example Breakdown:

p = Period.MIDTERM;

p.toString() → "MIDTERM"
p.ordinal() → 1
p.equals(Period.PRELIM) → false

👉 In short: parang may ranking system yung enums.

🔹 3. STATIC METHODS IN ENUM

These are called using the enum type itself, not the variable.

📌 Methods:

Method	Purpose
`valueOf()`	Converts String → Enum
`values()`	Returns all enum values

🔍 Example:

Period.valueOf("PRELIM"); // returns PRELIM

for(Period p : Period.values()) {
 System.out.print(p);
}

👉 Loop through all values — parang list lang.

🧠 Real-Life Use:

User input → convert to enum (like grading system)

“Midterm” → becomes MIDTERM

🔹 4. ENUM + SWITCH STATEMENT

Enums work perfectly with switch 😎

🍕 Example:

enum Size {REGULAR, LARGE, PARTY};

switch(s) {
 case REGULAR: ...
 case LARGE: ...
 case PARTY: ...
}

🧠 Real-Life Analogy:

Parang menu selection:

REGULAR → ₱381
LARGE → ₱602
PARTY → ₱799

👉 Clean, readable, no magic strings 👌

⚡ Key Concept: TYPE-SAFE

👉 Meaning:

Only valid values are allowed.

No weird inputs. No nonsense.

🔹 5. NESTED CLASSES

📌 What is a Nested Class?

A class inside another class.

👉 Parang:

“Class within a class” (yes, Java Inception 😵)

🎯 Why Use It?

Better organization
Related classes are grouped together
Easier to maintain

💡 In short, ganito lang ‘yan: ginagamit mo siya kapag tightly related yung classes.

🔹 6. TYPES OF NESTED CLASSES

Type	Description
Static Member Class	Access only static members
Inner Class	Needs instance, full access
Local Class	Inside a method
Anonymous Class	No name (one-time use)

🧠 Easy Memory Trick:

S.I.L.A.

Static
Inner
Local
Anonymous

🔹 7. INNER CLASS (IMPORTANT)

📌 Example (Real Estate System):

Outer class:

class RealEstateListing

Inner class:

private class HouseData

👉 According to page 4, the inner class stores address and square feet, while the outer class stores listing info

🧠 Why Inner Class?

Used ONLY inside the outer class
Keeps data private and organized

🔐 Access Rules:

Feature	Inner Class
Can access outer class private data?	✅ YES
Can be accessed outside?	❌ (if private)

⚠ Important Note:

Inner classes are not commonly used
If needed elsewhere → better as separate class

🧠 QUICK SECTION SUMMARY

ENUM:

👉 Fixed values only

👉 Type-safe

👉 Has built-in methods

NESTED CLASSES:

👉 Class inside a class

👉 Improves organization

👉 Used when tightly related

🔥 FINAL RECAP + MEMORY TRICKS

🧠 ENUM = “LIMITED CHOICES ONLY”

Think:

“Menu items lang — walang freestyle.”

🧠 ENUM METHODS (Mnemonic: TOEC)

ToString
Ordinal
Equals
CompareTo

🧠 STATIC ENUM METHODS:

valueOf() → string to enum
values() → all values

👉 Think: “VALUE & VALUES” = convert + list

🧠 NESTED CLASSES:

Think:

“Helper class inside main class”

🧠 TYPES (SILA):

Static
Inner
Local
Anonymous

💬 FINAL WORD (Gen Z Mode)

If you remember nothing else:

👉 Enums = controlled values (safe coding)

👉 Nested classes = organized code (clean structure)