Editing Comparison of C Sharp and Java (section)

==== Extension methods and default methods ====
Using a special ''this'' designator on the first parameter of a method, C# allows the method to act as if it were a member method of the type of the first parameter. This ''extension'' of the foreign class is purely syntactical. The extension method must be declared {{mono|static}} and defined within a purely static class. The method must obey any member access restriction like any other method external to the class; thus static methods cannot break object encapsulation.<ref>{{cite web
| url=http://www.hanselman.com/blog/HowDoExtensionMethodsWorkAndWhyWasANewCLRNotRequired.aspx
| title=How do Extension Methods work and why was a new CLR not required?
| first=Scott|last=Hanselman
| date=4 April 2008
| quote=''Extension methods are a really nice syntactic sugar. They're not really added to the class, as we can see, but the compiler makes it feel like they are''
| access-date=29 March 2014}}</ref><ref>{{cite web
| url=http://msdn.microsoft.com/en-us//library/bb383977.aspx
| title=Extension Methods (C# Programming Guide)
| publisher=[[Microsoft]]
| year=2013
| quote=''Extension methods are defined as static methods but are called by using instance method syntax''
| access-date=29 March 2014}}</ref> The "extension" is only active within scopes where the namespace of the static host class has been imported.

Since Java 8, Java has a similar feature called ''default methods'', which are methods with a body declared on interfaces. As opposed to C# extension methods, Java default methods are instance methods on the interface that declare them. Definition of default methods in classes that implement the interface is optional: If the class does not define the method, the default definition is used instead.

Both the C# extension methods and the Java default methods allow a class to override the default implementation of the extension/default method, respectively. In both languages this override is achieved by defining a method on the class that should use an alternate implementation of the method.

C# scope rules defines that if a matching method is found on a class, it takes precedence over a matching extension method. In Java any class declared to implement an interface with default method is assumed to have the default methods implementations, ''unless'' the class implements the method itself.