I know two of it can be used to send http request and get the response from the server, then we can parse into Json object if we want. So:
Retrofit 2 and Volley are both great networking libraries for modern Android apps, but each has its own strengths that are worth weighing for critical projects. Use Retrofit if your use-case is a standard REST API with JSON responses and not too many custom requirements in terms of caching, request prioritization, retries, etc. Use Volley if you have unusual / fine-grained requirements, or if you anticipate needing a lot of flexibility from your networking layer in the future at the cost of more code. Use neither if you're downloading large files or streaming -- for that, use DownloadManager instead.
Note: HttpClient is deprecated Now
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