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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 Collection interface is a subinterface of java.lang.Iterable, so any Collection may be the target of a for-each statement. (The Iterable interface provides the iterator() method used by for-each statements.) All Collections have an java.util.Iterator that goes through all of the elements in the Collection. Collection is generic.
When primitive and value types are used as generic arguments, they get specialized implementations, allowing for efficient generic collections and methods. As in C++ and Java, nested generic types such as Dictionary<string, List<int>> are valid types, however are advised against for member signatures in code analysis design rules. [29]
In the Java programming language, the wildcard? is a special kind of type argument [1] that controls the type safety of the use of generic (parameterized) types. [2] It can be used in variable declarations and instantiations as well as in method definitions, but not in the definition of a generic type.
As for migration compatibility, new generic collection classes and interfaces were developed that supplemented the non-generic .NET 1.x collections rather than replacing them. In addition to generic collection interfaces, the new generic collection classes implement the non-generic collection interfaces where possible.
The Java syntax has been gradually extended in the course of numerous major JDK releases, and now supports abilities such as generic programming and anonymous functions (function literals, called lambda expressions in Java). Since 2017, a new JDK version is released twice a year, with each release improving the language incrementally.
Collections of data objects are typically stored in Java collection classes, such as implementations of the Set and List interfaces. Java generics, introduced in Java 5, are also supported. Hibernate can be configured to lazy load associated collections. [2]: 289–293 Lazy loading is the default as of Hibernate 3.
Java, C#, Visual Basic .NET and Delphi have each introduced "generics" for parametric polymorphism. Some implementations of type polymorphism are superficially similar to parametric polymorphism while also introducing ad hoc aspects. One example is C++ template specialization.