Understanding Java Access Modifiers: Essential for Cross‑Platform OOP Development

Java Access Modifiers

Encapsulation hides an object's member variables and implementation details; access modifiers control how these members can be accessed from other code.

Java defines four access modifiers:

public : the most permissive level; any class, regardless of package or inheritance relationship, can access a public member or class.

protected : accessible to classes in the same package and to subclasses in other packages; it is commonly used when a method is intended to be overridden by derived classes.

default (no explicit modifier, also called “friendly”): accessible only to classes within the same package.

private : accessible only within the declaring class; it is typically applied to fields to enforce strict encapsulation.

Additional rules governing public classes:

Only one public class may appear in a single .java source file.

If a class is declared public, its name must exactly match the source file name (e.g., a public class Car must be stored in Car.java).

These constraints help maintain clear package organization and reliable encapsulation in Java applications.