Provides a representation of all the components, both visual and non-visual, in your application as a tree hierarchy. The additional toolbar buttons provide convenient access to common commands, such as choosing between Selection and Connection modes, aligning components, setting component auto-resizing behavior, and previewing forms. The toolbar’s Source button enables you to view a class’s source code, the Design button allows you to view a graphical view of the GUI components, the History button allows you to access the local history of changes of the file. The GUI Builder’s primary window for creating and editing Java GUI forms.