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In Java there are four types of nested class: . Static. Static member class, also called static nested classes [1] – They are declared static.Like other things in static scope (i.e. static methods), they do not have an enclosing instance, and cannot access instance variables and methods of the enclosing class.
Java enables classes to be defined inside methods. These are called local classes. When such classes are not named, they are known as anonymous classes (or anonymous inner classes). A local class (either named or anonymous) may refer to names in lexically enclosing classes, or read-only variables (marked as final) in the lexically enclosing method.
An inner class is typically neither associated with instances of the enclosing class nor instantiated along with its enclosing class. Depending on the language, it may or may not be possible to refer to the class from outside the enclosing class. A related concept is inner types, also known as inner data type or nested type, which is a ...
A nested function can use identifiers (i.e. the name of functions, variables, types, classes) declared in any enclosing block, except when they are masked by inner declarations with the same names. A nested function can be declared within a nested function, recursively, to form a deeply nested structure.
Classes are divided into top-level and nested. Nested classes are classes placed inside another class that may access the private members of the enclosing class. Nested classes include member classes (which may be defined with the static modifier for simple nesting or without it for inner classes), local classes and anonymous classes.
For object values, the reference cannot change. This allows the Java compiler to "capture" the value of the variable at run-time and store a copy as a field in the inner class. Once the outer method has terminated and its stack frame has been removed, the original variable is gone but the inner class's private copy persists in the class's own ...
C# has a static class syntax (not to be confused with static inner classes in Java), which restricts a class to only contain static methods. C# 3.0 introduces extension methods to allow users to statically add a method to a type (e.g., allowing foo.bar() where bar() can be an imported extension method working on the type of foo).
[citation needed] The Java programming language deals with it by requiring that context used by nested functions in anonymous inner and local classes be declared final, and context used by lambda expressions be effectively final. C# and D have lambdas (closures) that encapsulate a function pointer and related variables.