Is it possible to auto-generate Javadoc comments for each method in one class in IntelliJ IDEA?
Yes.
Under Tools
you have Generate JavaDoc
. Read about it in the official site.
In addition you may (Intellij 15):
Position caret above a method name, type /** and press Enter to let IntelliJ IDEA automatically generate JavaDoc stubs for this method
Edit: You can use the action Fix doc comment
. It doesn't have a default shortcut, but you can assign the Alt+Shift+J shortcut to it in the Keymap, because this shortcut isn't used for anything else.