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read-only interface comparison table

Subject	have solution	have context	have forces	have problem	has definition	have antipatterns	is a subtopic of	is a kind of	is an instance of
design pattern		a context	one or more forces	a sentence or two explaining the main difficulty being tackled	A pattern useful for the design of software	zero or more antipatterns - solutions that are inferior or do not work in this context with the reason for their rejection	6.1 - Introduction to Patterns	pattern
read-only interface	Create a «Mutable» class as you would create any other class, except make sure it is not public; this ensures that it can be accessed only from its package. All classes that need to modify the class, often called «Mutator» classes, must be put in this package. Then create a public interface we will call the «ReadOnlyInterface», that has only the read-only operations of «Mutable» - i.e. only operations that get its values. The «Mutable» class implements the «ReadOnlyInterface».	You sometimes want certain privileged classes to be able to modify attributes of objects that are otherwise immutable.	Programming languages such as Java allow you to control access by using the public, protected and private keywords. However making access public makes it public for both reading and writing.	How do you create a situation where some classes see a class as read-only (i.e. the class is immutable) whereas others are able to make modifications?	A pattern in which an interface is used to restrict which classes have privileges to call update methods of a class	making the read only class a subclass of the «Mutable» class, overriding all methods that modify properties, such that they throw an exception	6.11 - The Read-Only Interface Pattern		design pattern

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