My book is a Chinese version.
In page 82(Chapter III), it says, when we use the "switch" sentence, we always should add the "break" when we finish one case, just like "TrySwitch.java".

But in page 238(Chapter VI), when the author talks about the enumeration in class, there are many programs, such like TryEnumeration.java, JacketSize.java. But in JacketSize, it used the "switch" sentence, but it doesn't add the "break", and it runs correctly. Why is it?

when you've multiple case block in a switch in order to stop continuing with the next line after running one case block you'll use break so that control skips all the other case blocks. if you've a case at the end and if you dont use the break for it then it doesn't matter as there are not other case blocks it'll execute after completing the current one in that case you can ignore it. That is why the default block mostly doesn't have break statements.

- Rakesh