Here are the shortcuts I use in my daily Java routine:

• sout: System.out.println
• souf: System.out.printf
• fori: for loop
• itar: for loop
• iter: foreach loop
• ALT+ENTER: Gives suggestions
• ALT+INSERT: What kind of construction to implement with the code
• CTRL+F5: Refreshes the console
• CTRL+Q: Shows documentation offline
• SHIFT+F1: Shows documentation online
• CTRL+D: Copying the previous row on the current one (the cursor must be on the previous one)
• CTRL+Y: Put the cursor on the row + CTRL+Y and it will delete it (the row)
• CTRL+SHIFT+ARROW UP/ARROW DOWN: Moves the current row (on which is the cursor) to the upper or the row down below - inter-changing them with each other
• CTRL+ALT+T: - Surround the code + CTRL+ALT+T - it will show you which options you can use/implement (IF, TRY-CATCH BLOCK, ETC.) - Surround the code with... (Live templates)
• CTRL+ALT+L: Formatting the code - making it beautiful 🙂
• F2: Shows where is the error in the code - the cursor will go directly on the error
• RIGHT CLICK >> Local History >> Show History: Shows the last changes (history - and you can choose which version to use)
• CTRL+P: Put the cursor between the brackets (|) + CTRL+P: it will show you which parameters (values) you can use/put inside of the brackets ()
• SHIFT+F6: Renames all variables at once (FIRST HAVE TO CHOOSE the variable you want to change/rename + SHIFT+F6)
• Double-press Shift: Searches everywhere
• CTRL+J: Inserts a live template
• CTRL+ALT+J: Surrounds with a live template
• CTRL+R: Find and replace
• CTRL+E: Opens the recent file(s)
• CTRL+J: Shows the available shortcodes
• CTRL+SLASH (/): Commenting the code or line(s) of code; Remove comment - press again: CTRL+SLASH (/)

Here's one useful page as well: https://www.jetbrains.com/help/idea/2016.1/keyboard-shortcuts-you-cannot-miss.html

You can also easily create your own Live Templates, shortcodes and abbreviations in IntelliJ (and JetBrains products);

This video is useful (IntelliJ IDEA Tips and Tricks):

If you are teaching someone Java on IntelliJ you can use one very useful presentation plugin from the JetBrain repository called Presentation Assistant: https://plugins.jetbrains.com/plugin/7345

Just go to Help >> Find Action... >> type plugins >> choose  it >> choose Browse repositories >> type presentation assistant >> install it