Source file structure
By default, IntelliJ IDEA shows all classes, methods, and other elements of the current file. To toggle the elements you want to show, click the corresponding buttons on the Structure tool window toolbar. For example:
Click to show class fields.
Click to show inherited members.
Click to show lambdas.
Show class members in the Project tool window
Right-click the Project tool window title bar and select Show members from the context menu.