You can explore the hierarchy of parent and children classes of a selected class in the Hierarchy tool window.

Note that the Hierarchy tool window only becomes available, when you build the class hierarchy, as described below.

To build the hierarchy of classes
  1. Select the desired class in the Project tool window, or open it in the editor.
  2. On the main menu, choose Navigate | Type Hierarchy or press ⌃H or ⌃H⌃H or ⌃HF4 or F4⌥ H, ⌥H or ⌥H^ H, ⌃H or ⌃H.

The class hierarchy appears in the Hierarchy tool window.

java_type_hierarchy