A class library contains [[Class (computer science)|classes]] that can be used to create [[object (computer science)|objects]].
'''Class libraries''' are the rough OOP equivalent of older types of code libraries. They contain [[Class (computer science)|classes]], which describe characteristics and define actions ([[Method (computer science)|methods]]) that involve objects. Class libraries are used to create [[Instance (computer science)|instances]], or objects with their characteristics set to specific values. In some OOP languages, like [[Java (programming language)|Java]], the distinction is clear, with the classes often contained in library files (like Java's [[jar (file format)|JAR file format]]) and the instantiated objects residing only in memory (although potentially able to be made [[Persistence (computer science)|persistent]] in separate files). In others, like [[Smalltalk]], the class libraries are merely the starting point for a [[system image]] that includes the entire state of the environment, classes and all instantiated objects.
In [[Java (programming language)|Java]], for example, classes are contained in [[jar (file format)|JAR files]] and objects are created at runtime from the classes. However, in [[Smalltalk]], a class library is the starting point for a [[system image]] that includes the entire state of the environment, classes and all instantiated objects.
Today most class libraries are stored in a [[package repository]] (such as Maven Central for Java). Client code explicitly declare the dependencies to external libraries in [[Software build|build]] configuration files (such as a Maven Pom in Java).▼
▲Today mostMost class libraries are stored in a [[package repository]] (such as Maven Central for Java). Client code explicitly declare thespecifies dependencies to external libraries in [[Software build|build]] configuration files (such as a Maven Pom in Java).
