Java 8 | Clean Code | How to use computeIfAbsent method to prepare multi-value HashMap?

Small tutorial to explain how to use computeIfAbsent method to write one liner code instead of typical way of checking the presence of key and then adding the value accordingly in a multi-value HashMap, and this way we can write clean code and avoid if-else condition too!

[sachinsoni]

Thanks for saving time and at the same time explaining the concept very well