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Java does not have uninitialized variables. Fields of classes and objects that do not have an explicit initializer and elements of arrays are automatically initialized with the default value for their type (false for boolean, 0 for all numerical types, null for all reference types). [4]
C++ allows namespace-level constants, variables, and functions. In Java, such entities must belong to some given type, and therefore must be defined inside a type definition, either a class or an interface. In C++, objects are values, while in Java they are not. C++ uses value semantics by default, while Java always uses reference semantics. To ...
The C++ standard library instead provides a dynamic array (collection) that can be extended or reduced in its std::vector template class. The C++ standard does not specify any relation between new / delete and the C memory allocation routines, but new and delete are typically implemented as wrappers around malloc and free. [6]
Elements of a newly created array may have undefined values (as in C), or may be defined to have a specific "default" value such as 0 or a null pointer (as in Java). In C++ a std::vector object supports the store, select, and append operations with the performance characteristics discussed above. Vectors can be queried for their size and can be ...
C++11 extended this further, to make classes act identically to POD objects in many more cases. ^c pair only ^d Although Perl doesn't have records, because Perl's type system allows different data types to be in an array, "hashes" (associative arrays) that don't have a variable index would effectively be the same as records.
If a class does not specify its superclass, it implicitly inherits from java.lang.Object class. Thus all classes in Java are subclasses of Object class. If the superclass does not have a constructor without parameters the subclass must specify in its constructors what constructor of the superclass to use. For example:
In object-oriented computer programming, a null object is an object with no referenced value or with defined neutral (null) behavior.The null object design pattern, which describes the uses of such objects and their behavior (or lack thereof), was first published as "Void Value" [1] and later in the Pattern Languages of Program Design book series as "Null Object".
In computer programming, lazy initialization is the tactic of delaying the creation of an object, the calculation of a value, or some other expensive process until the first time it is needed.