Understanding access modifiers in java

Access modifiers

Access modifiers in Java are keywords that define the accessibility (visibility) of classes, fields (variables), methods, and constructors within a Java program. They control which parts of your code can access these elements and how they can be used. Here's a breakdown of the four main access modifiers:

1. Public:

• Members declared as public are accessible from anywhere in your program, regardless of the package or class they are in.
• This is the most permissive access modifier and should be used cautiously for elements that need to be widely accessible throughout your application.

Example:

public class PublicClass {
  public String publicField;
  public void publicMethod() {
    System.out.println("This is a public method!");
  }
}

2. Private:

• Members declared as private are only accessible within the class they are defined in.
• They are invisible to other classes, even within the same package.
• This is the most restrictive access modifier and promotes encapsulation by protecting internal implementation details.

Example:

class PrivateClass {
  private int privateField;
  private void privateMethod() {
    System.out.println("This is a private method!");
  }
}

3. Protected:

• Members declared as protected are accessible within the class they are defined in, as well as in subclasses of that class (even if the subclasses are in different packages).
• This allows controlled inheritance and sharing of implementation details between a class and its subclasses.

Example:

class ParentClass {
  protected String protectedField;
  protected void protectedMethod() {
    System.out.println("This is a protected method!");
  }
}

class ChildClass extends ParentClass {
  public void someMethod() {
    System.out.println(protectedField); // Accessing inherited protected field
    protectedMethod(); // Calling inherited protected method
  }
}

4. Default (Package-Private):

• If you don't explicitly use any access modifier, the member inherits the default access modifier, which is package-private.
• Members with default access are only accessible from classes within the same package.
• This provides a balance between visibility and encapsulation, allowing access within the same package but restricting access from outside.

Example:

package com.example;

class DefaultClass {
  String defaultField;
  void defaultMethod() {
    System.out.println("This is a default method!");
  }
}

// Another class in the same package can access these members
class SamePackageClass {
  public void someMethod() {
    DefaultClass obj = new DefaultClass();
    System.out.println(obj.defaultField);
    obj.defaultMethod();
  }
}

Choosing the Right Access Modifier:

• Use public sparingly, only for members that truly need to be accessed from anywhere.
• Favor private for internal implementation details to promote data hiding and encapsulation.
• Use protected for members that should be shared and potentially overridden in subclasses.
• Use default for members that should be accessible within the same package but hidden from outside packages.

By effectively using access modifiers, you can improve code organization, maintainability, and control the reusability of your classes and their components in Java.