C# vs Java - Access Modifiers

C#

There are 5 access modifiers in C#:

• public
• private
• protected
• internal
• protected internal

These are used in the declaration of classes, structs and members of classes or structs. The public access modifier allows access from anywhere, and should be used sparingly. It is best to use public only where a member will need to be accessed by a class that is not part of the same assembly or extends the applicable class. The public modifier is common in the declaration of classes or properties, as classes are often externally used and properties define getters and setters and thus aid encapsulation.

The private modifier is good for encapsulation, as it hides anything that should be inaccessible by another class. It is the most restrictive of access modifiers as only code in the same struct or class can access it, and is the default for class or struct members. The private modifier is commonly used on fields, but is also used on methods that may be called within public methods but shouldn't be accessible otherwise. By using the private modifier where possible we can help reduce the chance of other programmers calling the wrong method when they are using our class. It is important to note a class cannot be private unless it is nested within another class.

The protected modifier means that the type or member can only be accessed by code in the same class, or classes that inherit from it. Therefore, it is important to give careful thought to members you are considering declaring protected as if you release your code as a library, and other classes extend your class, and then you want to make a change to the member, your change may break code that uses your library. The protected modifier can be useful when declaring an abstract class, to ensure that classes which extend this abstract class have access to members which should be common amongst all classes that extend the abstract class.

The internal modifier is the default for classes and structs in C#, and is similar to package-visibility in Java. This modifier gives access to any code in the same project, and is commonly used to confine the use of a class to a project in a solution. Generally, a class' members have lower or equal accessibility to the class, but sometimes when an internal class extends a public class it may have public members that it has overridden from the base class.

Additionally, there is the protected internal access modifier. This basically means it can be accessed from code where it could be accessed from if the member was declared protected OR internal. Finally, it is important to note that interface members cannot be declared with an access modifier, this makes sense as the purpose of an interface is to allow another class to access another's members. Interfaces can either be internal or public.

Java

Java is quite similar to C#, so first we will outline the similarities in access modifiers:

• public behaves the same way in both C# and Java
• private behaves the same way in both C# and Java.
• protected behaves the same way in both C# and Java.

However, there are some differences. Firstly, by default classes or members of a class have package-visibility in Java which means that they can be accessed by code in the same package. Whereas, in C# default accessibility for a member is private and the default accessibility for a class in internal. Package-visibility is similar to internal visibility, except that in Java the package is represented physically by a directory and only code in the same directory can access something with package visibility. Whereas, with internal members any code in a project (not necessarily the same directory) can access it.

Finally, in Java there is no way to explicitly set package-visibility, and no way to allow for either protected or package-visibility access for the same member (as you do with protected internal in C#). Therefore, you have a lower level of control over the accessibility of classes and their members than you do in C#. C# is easier to modularize your code in, by using internal and having different projects in the same solution, and therefore I find it better suited for commercial work as it is easier to maintain the structure of a solution.