• A more precise explanation of how Jacoco calculates code coverage, directly from its manual: https://www.jacoco.org/jacoco/trunk/doc/counters.html.
• A nice set of slides from University of Edinburgh, based on Pezzè and Young’s book, Pezze and Young, Software Testing and Analysis: Process, Principles and Techniques, Wiley, 2007., Chapter 12: http://www.inf.ed.ac.uk/teaching/courses/st/2017-18/Ch12.pdf
• An interview with Marc Hoffman, key developer behind Jacoco: http://www.se-radio.net/2018/05/se-radio-episode-324-marc-hoffmann-on-code-test-coverage-analysis-and-tools/.

Further reading:

• Chapter 12 of Pezze and Young, Software Testing and Analysis: Process, Principles and Techniques, Wiley, 2007.