Access modifiers & encapsulation

public, protected, package-private, private — and why private fields with getters matter.

Controlling visibility

Java has four access levels, from broadest to narrowest:

Modifier	Same class	Same package	Subclass (any pkg)	Any class
`public`	yes	yes	yes	yes
`protected`	yes	yes	yes	no
(none — package-private)	yes	yes	no	no
`private`	yes	no	no	no

A member with no modifier is package-private (also called "default" access) — accessible within the same package only.

Encapsulation hides implementation details: make fields private and expose controlled access through public getters and setters:

public class BankAccount {
    private double balance;

    public double getBalance() { return balance; }

    public void deposit(double amount) {
        if (amount > 0) balance += amount;
    }
}

Benefits: the class can validate changes, change its internal representation later without breaking callers, and centralise logging or events.

Each level is a strict superset of the next: protected is package-private plus subclasses in other packages, which is exactly why protected is the wider of the two.