Intellij Idea How to add interface implementation to classes?

Question

For example I have many classes than implement my interface. After adding new method definition in the interface, how can I fast-add blank interface implementations for all that classes?

Answer 1

You can generate an implementation of an interface by moving the caret to the name of the interface and pressing option+return (on Mac) or ALT+Enter (on PC), then hovering over Implement interface and pressing return/Enter:

Please note that my caret can't be seen but it's between the h and a of Shape

IntelliJ will then prompt you for a class name and which methods to include in the implementation, then generate a class, like this: