What is a Class in Java?

A class is basically a definition, and contains the object's code. An object is an instance of a class. For instance, there is one java.lang.String class, but you can instantiate any number of distinct java.lang.String objects (instances). While a class defines the instance variables than an object has, the instantiated object itself actually contains those variables. An object is an instance of a class.

Defines the abstract characteristics of a thing (object), including the thing's characteristics (its attributes, fields or properties) and the thing's behaviors (the things it can do, or methods, operations or features). One might say that a class is a blueprint or factory that describes the nature of something. For example, the class Dog would consist of traits shared by all dogs, such as breed and fur color (characteristics), and the ability to bark and sit (behaviors). Classes provide modularity and structure in an object-oriented computer program. A class should typically be recognizable to a non-programmer familiar with the problem domain, meaning that the characteristics of the class should make sense in context. Also, the code for a class should be relatively self-contained (generally using encapsulation). Collectively, the properties and methods defined by a class are called members. 


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