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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 ...
Collection implementations in pre-JDK 1.2 versions of the Java platform included few data structure classes, but did not contain a collections framework. [4] The standard methods for grouping Java objects were via the array, the Vector, and the Hashtable classes, which unfortunately were not easy to extend, and did not implement a standard member interface.
In the Java Collections Framework, the class List<MyClass> represents an ordered collection of objects of type MyClass. Upper bounds are specified using extends : A List<? extends MyClass> is a list of objects of some subclass of MyClass , i.e. any object in the list is guaranteed to be of type MyClass , so one can iterate over it using a ...
That is, an enumeration of a set S is a bijective function from the natural numbers or an initial segment {1, ..., n} of the natural numbers to S. A set is countable if it can be enumerated, that is, if there exists an enumeration of it. Otherwise, it is uncountable. For example, the set of the real numbers is uncountable.
The types of objects that can be iterated across (my_list in the example) are based on classes that inherit from the library class ITERABLE. The iteration form of the Eiffel loop can also be used as a boolean expression when the keyword loop is replaced by either all (effecting universal quantification) or some (effecting existential ...
However, the compiler automatically transforms the code so that the list will "silently" receive objects, while the source code only mentions primitive values. For example, the programmer can now write list. add (3) and think as if the int 3 were added to the list; but, the compiler will have actually transformed the line into list. add (new ...
A snippet of Java code with keywords highlighted in bold blue font. The syntax of Java is the set of rules defining how a Java program is written and interpreted. The syntax is mostly derived from C and C++. Unlike C++, Java has no global functions or variables, but has data members which are also regarded as global variables.
For example, Java's numeric types are primitive, while classes are user-defined. A value of an atomic type is a single data item that cannot be broken into component parts. A value of a composite type or aggregate type is a collection of data items that can be accessed individually. [ 6 ]