Visibility modifiers (public, private, internal, protected) in Kotlin - Step-by-Step Execution

Concept Flow - Visibility modifiers (public, private, internal, protected)

Start: Define class or member

↓

Check modifier

↓

public

↓

Accessible everywhere

↓

Use member accordingly

↓

End

This flow shows how Kotlin decides who can access a class or member based on its visibility modifier.

Execution Sample

Kotlin

class Example {
    public val a = 1
    private val b = 2
    internal val c = 3
    protected val d = 4
}

Defines a class with four properties, each having a different visibility modifier.

Execution Table

Step	Member	Modifier	Accessible From	Explanation
1	a	public	Anywhere	Public means no restriction, accessible everywhere.
2	b	private	Only inside Example class	Private restricts access to inside the class only.
3	c	internal	Same module	Internal allows access within the same module.
4	d	protected	Example class and subclasses	Protected allows access in class and subclasses.
5	Access outside Example	Check each modifier	Only public and internal accessible if in same module	Private and protected not accessible outside class or subclass.
6	Access in subclass	Check protected	Protected accessible	Protected members accessible in subclass.
7	End	-	-	All visibility rules applied.

💡 Execution ends after checking all visibility rules for each member.

Variable Tracker

Member	Modifier	Accessible From
a	public	Anywhere
b	private	Only inside Example class
c	internal	Same module
d	protected	Example class and subclasses

Key Moments - 3 Insights

Why can't I access a private member from outside the class?

Private members are only accessible inside the class where they are declared, as shown in execution_table step 2.

What does internal mean and when can I access it?

Internal means the member is accessible anywhere inside the same module, but not outside it, as explained in step 3.

How is protected different from private?

Protected allows access in subclasses too, while private restricts access only to the class itself, as shown in steps 2 and 4.

Visual Quiz - 3 Questions

Look at the execution_table, which member can be accessed anywhere without restriction?

A b

B a

C c

D d

💡 Hint

Check step 1 in execution_table where 'a' is public and accessible anywhere.

At which step does the table explain that a member is accessible only inside the class?

A Step 3

B Step 4

C Step 2

D Step 1

💡 Hint

Look at step 2 where 'b' is private and accessible only inside the class.

If you try to access a protected member from outside the class and subclass, what happens?

A It is not accessible

B It depends on the module

C It is accessible

D It becomes internal

💡 Hint

Step 5 and 6 explain protected is accessible only in class and subclasses, not outside.

Concept Snapshot

Visibility modifiers in Kotlin:
- public: accessible everywhere
- private: accessible only inside the class
- internal: accessible within the same module
- protected: accessible in class and subclasses
Use them to control who can see or use your code parts.

Full Transcript

In Kotlin, visibility modifiers control access to classes and members. Public means anyone can access it. Private means only the class itself can access it. Internal means access is allowed within the same module. Protected means access is allowed in the class and its subclasses. This helps keep code safe and organized by controlling who can use what. The example class shows four properties each with a different modifier. The execution table traces where each is accessible. Key moments clarify common confusions about private, internal, and protected. The quiz tests understanding by asking about accessibility at different steps.