05 Access modifiers

1. Access modifiers in Java are keywords that set the accessibility (visibility) of classes, methods, and variables.
2. They determine how the members of a class can be accessed from other classes or packages.
3. There are four main access modifiers in Java

Modifier	Class	Package	Subclass (Same Package)	Subclass (Different Package)	Outside Package
public	Yes	Yes	Yes	Yes	Yes
protected	Yes	Yes	Yes	No	No
private	Yes	No	No	No	No
Default	Yes	Yes	Yes	No	No

1. Public

• Definition: The public access modifier allows a class, method, or variable to be accessible from any other class in any package.
• Usage: Used when you want to provide wide accessibility.

Example:

public class PublicClass {
    public int publicVariable; // Public variable
 
    public void publicMethod() { // Public method
        System.out.println("This is a public method.");
    }
}

2. Private

• Definition: The private access modifier restricts the visibility to the defining class only. Members declared as private cannot be accessed from outside the class.
• Usage: Used to encapsulate data and provide controlled access through public methods.

Example:

public class PrivateClass {
    private int privateVariable; // Private variable
 
    public void setPrivateVariable(int value) { // Public method to set private variable
        this.privateVariable = value;
    }
 
    public int getPrivateVariable() { // Public method to get private variable
        return privateVariable;
    }
}

3. Protected

• Definition: The protected access modifier allows visibility to the defining class, subclasses (inherited classes), and classes in the same package.
• Usage: Used when you want to allow access to members in subclasses and within the same package.

Example:

public class ProtectedClass {
    protected int protectedVariable; // Protected variable
 
    protected void protectedMethod() { // Protected method
        System.out.println("This is a protected method.");
    }
}

4. Default (Package-Private)

• Definition: If no access modifier is specified, the default access level (also known as package-private) is applied. Members with default access are accessible only within the same package.
• Usage: Used to restrict visibility to classes within the same package.

Example:

class DefaultClass { // No access modifier, hence default
    int defaultVariable; // Default variable
 
    void defaultMethod() { // Default method
        System.out.println("This is a default method.");
    }
}