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C++ is also more strict in conversions to enums: ints cannot be implicitly converted to enums as in C. Also, enumeration constants (enum enumerators) are always of type int in C, whereas they are distinct types in C++ and may have a size different from that of int. [needs update] In C++ a const variable must be initialized; in C this is not ...
The Java standard library provides utility classes to use with enumerations. The EnumSet class implements a Set of enum values; it is implemented as a bit array, which makes it very compact and as efficient as explicit bit manipulation, but safer. The EnumMap class implements a Map of enum values to object. It is implemented as an array, with ...
In languages supporting multiple inheritance, such as C++, interfaces are implemented as abstract classes. In languages without explicit support, protocols are often still present as conventions. This is known as duck typing. For example, in Python, any class can implement an __iter__ method and be used as a collection. [3]
A class consisting of only pure virtual methods is called a pure abstract base class (or pure ABC) in C++ and is also known as an interface by users of the language. [13] Other languages, notably Java and C#, support a variant of abstract classes called an interface via a keyword in the language. In these languages, multiple inheritance is not ...
Class and interface types Most types in a GObject application will be classes — in the normal object-oriented sense of the word — derived directly or indirectly from the root class, GObject. There are also interfaces, which, unlike classic Java-style interfaces, can contain implemented methods. GObject interfaces can thus be described as ...
Java explicitly distinguishes between interfaces and classes. In C++, multiple inheritance and pure virtual functions make it possible to define classes that function almost like Java interfaces do, with a few small differences. Java has both language and standard library support for multi-threading.
Forward-declaring enums is also possible in C++11. Formerly, enum types could not be forward-declared because the size of the enumeration depends on the definition of its members. As long as the size of the enumeration is specified either implicitly or explicitly, it can be forward-declared:
The factory method design pattern solves problems such as: How can an object's subclasses redefine its subsequent and distinct implementation? The pattern involves creation of a factory method within the superclass that defers the object's creation to a subclass's factory method.