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.
Click to show class fields.
Click to have protected class members shown in the tree.
Click to have private class members shown in the tree.
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 from the context menu.