Eclipse text cursor has changed and editor behaves differently

Maybe you pressed the insert key, which will change the Eclipse editor to Overwrite rather than Smart Insert (see the info bar at the bottom of the editor), and will change the cursor to a block rather than a vertical line?

Update: Thanks for clarification - see mikej's answer which is correct. I'll leave this answer in case anyone has the similar, related problem that I describe.

If nothing works, restart eclipse. That is what I did !

It sounds like you have accidentally switched from Smart Insert mode to Insert mode.

Press Ctrl + Shift + Insert or tick Smart Insert Mode on the Edit menu to switch back.

Smart Insert is the feature that automatically insert closing quotes and brackets when you type the opener and places semi-colons at the end of the line when you press semi-colon (if you have the preference for that enabled.)

Just double click on "Smart Insert" / "Overwrite" in eclipse status bar

For reference, I am adding image.