Disable code folding in IntelliJ Idea?

BEFORE:

AFTER:

To disable the folding icons and folding completely uncheck all checkboxes as depicted here:

Not sure what OP is asking, if one wishes to just hide the folding outline, then the @Phiter answer is correct.

However if one wishes to disable the actual code folding just uncheck boxes below the label Collapse by default.

For IntelliJ 15+ with default keyboard bindings

Press cmd+shift+A on a mac or ctrl+shift+A on windows, to search for an action, and type code folding. This pops up a menu with an option of 'Show code folding outline' and on the right of it is an off/on switch. You can change this with enter or just click on it.

The settings dialog is old-hat these days.

Go to File -> Settings -> Editor -> General -> Code Folding

Uncheck Show code folding outline.