Why does fall-through exist in switch at all, and how do you exploit it deliberately versus accidentally?

Fall-through lets multiple case labels share a body, which is useful for grouping — for instance MONDAY, TUESDAY, ... all falling into a 'weekday' branch.

The danger is accidental fall-through from a forgotten break, which silently executes the next case; static analyzers and -Xlint flag it. The Java 14 arrow form removes fall-through entirely and supports comma-separated labels (case MONDAY, TUESDAY ->), giving the grouping benefit without the footgun.