What is the difference between public, protected, package-private and private in Java?

 

In Java, access modifiers (public, protected, package-private/default, and private) control the visibility and accessibility of classes, methods, and fields within different scopes. Here's an explanation of each modifier with examples:

1. public:

   • Members declared as public are accessible from any class and package.
   • There are no restrictions on access.

   java

public class PublicExample {
    public int publicVar = 10;
    public void publicMethod() {
        System.out.println("This is a public method.");
    }
}

protected:

• Members declared as protected are accessible within the same package and subclasses (even if the subclass is in a different package).
• Subclasses can access protected members of their superclass.

java

class Parent {
    protected int protectedVar = 20;
}

public class Child extends Parent {
    public void accessProtectedVar() {
        System.out.println("Protected var from Child: " + protectedVar);
    }
}

Package-Private (Default):

• If no access modifier is specified, the member is package-private (default).
• Members are accessible only within the same package.

java

class PackagePrivateExample {
    int packagePrivateVar = 30;
}

private:

• Members declared as private are accessible only within the same class.
• They are not visible or accessible from any other class or package.

java

4. public class PrivateExample {
       private int privateVar = 40;
       private void privateMethod() {
           System.out.println("This is a private method.");
       }
   }
   

Remember, access modifiers apply not only to classes and methods but also to fields. The access level of a member affects where it can be accessed from and provides encapsulation by restricting direct access.

Example: Putting It All Together:

java

package com.example;

class Parent {
    int packagePrivateVar = 20;
    protected int protectedVar = 30;
    private int privateVar = 40;
}

public class Child extends Parent {
    public void accessMembers() {
        System.out.println("Package-Private Var: " + packagePrivateVar); // Accessible because in the same package
        System.out.println("Protected Var: " + protectedVar); // Accessible because it's a subclass
        // System.out.println("Private Var: " + privateVar); // Not accessible from Child
    }

    public static void main(String[] args) {
        Child child = new Child();
        child.accessMembers();
    }
}

In this example, the Child class inherits the protected member from its Parent class and can access it. The package-private member is also accessible because the classes are in the same package. However, the private member is not accessible from Child.