Broken Link Checker written in Java.
The program uses multithreading, retries if it is unable to connect to a webpage or gets a 429 HTTP response code ("too many requests"), and gives a report at the end showing each link tried, along with the result.
If you have gradle installed (on a Mac with homebrew, this is just brew update && brew install gradle), you can build an executable .jar file by first cloning the project, then running this command inside the project root:
gradle fatJar
The jar is saved to build/libs/blic.jar, so to run it, do:
java -jar build/libs/blic.jar [url to test]