Access modifiers

1 Learn

Access modifiers control who can see a class member.

public — everywhere. private — only inside the same class. protected — same package, plus subclasses in other packages. default (no keyword) — only inside the same package.

A good habit: keep fields private and expose only the methods others need.

Want more detail? Open the full lesson

2 See the Code

Java

class Locker {
    public String owner = "Ananya";
    protected int size = 2;
    int floor = 1;          // default (package) access
    private String pin = "4321";

    private boolean check(String p) { return pin.equals(p); }

    public void open(String p) {
        System.out.println(check(p) ? "Opened" : "Wrong PIN");
    }
}

public class Hostel {
    public static void main(String[] args) {
        Locker l = new Locker();
        System.out.println(l.owner);
        l.open("1111");
        l.open("4321");
        // l.pin  -> compile error: pin is private
    }
}

owner is public, so main can read it.
pin and check() are private, used only inside Locker.
open() is the public way in.

Output

Ananya
Wrong PIN
Opened

3 Practice

Draw a table of the four modifiers and tick where each is visible: same class, same package, subclass, everywhere.

Try it in your own Java setup or write it in the Practice Notebook.

4 Quick Check

1. A member with no modifier is visible...
2. Most restrictive modifier?

Step 5

Answer and check the Quick Check above to unlock this.

Day 25