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The Java collections framework supports generics to specify the type of objects stored in a collection instance. In 1998, Gilad Bracha, Martin Odersky, David Stoutamire and Philip Wadler created Generic Java, an extension to the Java language to support generic types. [4] Generic Java was incorporated in Java with the addition of wildcards.
The "generic programming" paradigm is an approach to software decomposition whereby fundamental requirements on types are abstracted from across concrete examples of algorithms and data structures and formalized as concepts, analogously to the abstraction of algebraic theories in abstract algebra. [6]
The above examples are particularly dedicated to this purpose. A large number of other languages, ... Java (generic, imperative, object-oriented (class-based), ...
Early versions of Java and C# did not include generics, also termed parametric polymorphism. In such a setting, making arrays invariant rules out useful polymorphic programs. For example, consider writing a function to shuffle an array, or a function that tests two arrays for equality using the Object. equals method on the elements. The ...
Unlike arrays (which are covariant in Java [2]), different instantiations of a generic type are not compatible with each other, not even explicitly. [2] For example, the declarations Generic<Supertype> superGeneric; Generic<Subtype> subGeneric; will cause the compiler to report conversion errors for both castings (Generic<Subtype>)superGeneric and (Generic<Supertype>)subGeneric.
Typically a generic function is an instance of a class that inherits both from function and standard-object. Thus generic functions are both functions (that can be called with and applied to arguments) and ordinary objects. The book The Art of the Metaobject Protocol explains the implementation and use of CLOS generic functions in detail.
In the following Java example cats and dogs are made subtypes of pets. The procedure letsHear() accepts a pet, but will also work correctly if a subtype is passed to it: abstract class Pet { abstract String speak (); } class Cat extends Pet { String speak () { return "Meow!"
Pizza is an open-source superset of Java 1.4, prior to the introduction of generics for the Java programming language.In addition to its own solution for adding generics to the language, Pizza also added function pointers and algebraic types with case classes and pattern matching.