Some time ago I programmed a proxy checker quite useful when you have a large list of proxies that you don't know if they work or not.
It is written in Java, so we will need a JRE machine installed. Running it is very easy, simply:
java -jar "jarname"
At the start of the program you have to specify the path of the proxies in the system, which is a txt in which each line is a proxy, example.
Enjoy!
Git repository:

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