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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 JavaScript, there are 7 primitive data types: string, number, bigint, boolean, symbol, undefined, and null. [19] Their values are considered immutable. These are not objects and have no methods or properties; however, all primitives except undefined and null have object wrappers. [20]
A Java logging framework is a computer data logging package for the Java platform. This article covers general purpose logging frameworks. Logging refers to the recording of activity by an application and is a common issue for development teams. Logging frameworks ease and standardize the process of logging for the Java platform.
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]
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 ...
In Java—and similar languages modeled after it, like JavaScript—it is possible to execute code even after return statement, because the finally block of a try-catch structure is always executed. So if the return statement is placed somewhere within try or catch blocks the code within finally (if added) will be executed.
Mixins are typically used to add the same methods to multiple classes. For example, class UnicodeConversionMixin might provide a method unicode_to_ascii() when included in class FileReader and class WebPageScraper, which do not share a common parent. Abstract classes cannot be instantiated into objects; they exist only for inheritance into ...
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: