Without an interface for the Toolkit class developers are forced to either implement their own interface or inject an implementation (Toolkit class) rather than an interface into their classes. Including ToolkitInterface in the package enables developers to "program to an interface, not an implementation."
Without an interface for the Toolkit class developers are forced to either implement their own interface or inject an implementation (Toolkit class) rather than an interface into their classes. Including ToolkitInterface in the package enables developers to "program to an interface, not an implementation."