MJ#25: Access Modifiers in Java

n Java, access modifiers are keywords that define the visibility and accessibility of classes, methods, and variables. They control which other classes can access a particular class, method, or variable. There are four main access modifiers in Java:

1. Default (Package-Private):
   • If no access modifier is specified, the default access level is package-private. This means that the class, method, or variable is accessible within the same package but not outside of it.

class Example {

    int x; // Package-private variable

    void method() { // Package-private method

        // ...

    }

}

Public:

• The public access modifier makes the class, method, or variable accessible from anywhere. This includes other packages.

public class PublicExample {

    public int y; // Public variable

    public void publicMethod() { // Public method

        // ...

    }

}

Private:

• The private access modifier restricts the visibility to only within the class where it is declared. It is not accessible from outside the class, including subclasses.

public class MyClass {

    private int z; // Private variable

    private void privateMethod() { // Private method

        // ...

    }

}

Protected:

• The protected access modifier allows access within the same package, as well as in subclasses (even if they are in different packages).

package com.example;



public class ParentClass {

    protected int protectedVariable; // Protected variable

    protected void protectedMethod() { // Protected method

        // ...

    }

}

package com.example.subpackage;



public class ChildClass extends ParentClass {

    void accessProtected() {

        protectedVariable = 10; // Accessing protected variable from the superclass

        protectedMethod(); // Accessing protected method from the superclass

    }

}

Here’s a summary of the access permissions for each access modifier:

Access Modifier	Within Class	Within Package	Outside Package (Subclass)	Outside Package (Non-subclass)
Default	Yes	Yes	No	No
Public	Yes	Yes	Yes	Yes
Private	Yes	No	No	No
Protected	Yes	Yes	Yes	No

It’s important to choose the appropriate access level based on the design and encapsulation principles to ensure proper data hiding and abstraction in your Java programs.