库、存储库、包和文件夹之间有什么区别？

Question

I was wondering whether there is any real technical difference between these things, or whether the difference is only semantic? It seems to me that they are all just places for storing other files.

Background: I am learning Java

Best wishes,

Patrick

Answer 1

On the differences between a library, repository, package and folder:

A library is a set of functionality that is packaged together for easy consumption. There is no big difference between a library and a framework or an engine, they all fulfill similar functionalities and the differences are subtle semantics.

Libraries are usually packaged -- either as JAR or as a Maven artifact, so that they can be easily used by another end user.

A package in Java in another name for namespace . Packages fulfill the role of disambiguating classes and organizing them. Yes, when you program in your IDE they are mapped 1:1 to folders in the file system - but that is just an implementation detail. In C# for example, namespaces do not map 1:1 to folders.

Repositories again are ambiguous. A repository is a location where something is stored. In terms of source code, this is often usually a version controlled repository like a git repo, mercurial repo or svn repo.

But other types of repositories exist. A Maven repository for example hosts machen artifacts - which can be used as a dependency in your POM.

Overall, you'll find the word repository in many places. Its the generic term for a place where something is stored. This can be a UserRepository in your own code, for example. Its not uncommon to see XXXRepository as class name.

Folders on file systems are just a means to an end, just like Key-Value stores and SQL databases. They aren't the organizational units Java devs usually are concerned with, except when actually doing file I/O.

Answer 2

What is often referred to as a library is generally a set of functionalities that you can import into your software with an import statement, like so:

import coolLibrary

You do this in order to not have to implement that functionality yourself. There are different terms in use for this in different contexts/programming languages, by the way.

A repository is a place where code and related resources are stored. This can be on your local file system or online. What separates this from a folder is that repositories, functionality for which is provided by tools like git , usually come with some archiving and version control tools.

A package is simply a group of related classes in Java. They're used to organize projects. The IDE of your choice will allow you to make use of this.