Maybe you entered Vim emulator as said. Maybe only by mistake :).
Control-V is a frequently used shortcut. And Control-Alt_V is the shortcut to enable Vim mode so you can see the problem...
How to know in five seconds: type a ":" (colon) and if the cursor jump to end of the screen, that is vim. If so enter q
to quit and then Control-Alt-V
(on windows) to go back to IDEA standard mode.
vi is a powerful text editor since ever. But only if you pretend and know how to use it... There is even a warning on the IDEA install saying like "do not install unless you are familiar with Vim" in yellow bold text, iirc.
[Follows historic data, that you may find boring off-topic or interesting]
Today's editors opens the code in edit mode right away so you can start typing over existing code. Vim
by the other hand opens the code in, let us say, browsing mode: there is a set of navigation keys to browse the code. Everything you type is supposed to be a command. When you want to edit you enter INSERT mode and then you can type new text. Only then.
Just for more historic data: vi navigation mode is great for studying code you do not know, using IDEA, since it does not change the text unless you tell it to, and some vi commands are clever.
One example:
"/"
(forward slash) is one search command, and "z"
is a smart scroll command so that:
/setCellFactory
will search for the next match of "setCellFactory" and put the cursor there
Then if you type "z"
the code will be positioned so that line is the first on screen. And if you type "."
the line will be at the middle. And if you type "-"
that line will be at the last position at the screen. And you can use these commands again and again. And new slash will go for the next match, like F3
This "z" thing is a feature I miss in Visual Studio, IDEA, Eclipse, Word, WordPad: these commands to scroll text AROUND a pattern... /pattern, z, z., z-. The alternative is the mouse wheel...
I am used to vi since the 80's and is the editor I still use today on Linux terminals so when this happened to me on IDEA I was lucky to remember and suspect of that on the first time.
Sorry if these details are boring