Java provides four access modifiers to control the visibility of classes, methods, and fields. These modifiers are public, private, protected, and the default (package-private) when no modifier is specified. Each defines a different level of access.

1. public

• Visibility: Accessible from any other class in any package.
• Applicable to: Classes, interfaces, methods, and fields.
• Example:

public class Example {
    public int publicField;
    public void publicMethod() { }
}

2. private

• Visibility: Accessible only within the same class.
• Applicable to: Methods, fields, and inner classses (but not top-level classes).
• Example:

public class Example {
    private int privateField;
    private void privateMethod() { }
}

3. protected

• Visibility: Accessible within the same package and by subclasses (evenif they are in different packages).
• Applicable to: Methods, fields, and inner classes (but not top-level classes).
• Example:

public class Example {
    protected int protectedField;
    protected void protectedMethod() { }
}

4. Default (Package-Private)

• Visibility: Accessible only within the same package (no explicit modifier).
• Applicable to: Classes, interfaces (except nested), methods, and fields.
• Example:

class Example {
    int defaultField;
    void defaultMethod() { }
}

Summary Table

Choosing the correct access modifier helps enforce encapsulation, reduces unintended dependencies, and clarifies the intended usage of your API.