update READMEs

README.md

@@ -19,9 +19,9 @@ objects).
  - [Bridge], implementation of an object 
  - [Composite], structure and composition of an object
  - [Decorator], responsibilities of an object without subclassing
- - [Façade], todo
+ - [Façade], interface to a subsystem
- - [Flyweight], todo
+ - [Flyweight], storage costs of objects
- - [Proxy], todo
+ - [Proxy], how an object is accessed (its location)
 - Behavioral Patterns
  - [Chain of Responsibility], todo
  - [Command], todo

facade/README.md

@@ -0,0 +1,11 @@
+## Fa<46>ade
+
+Provide a unified interface to a set of interfaces in a subsystem. Facade
+defines a higher-level interface that makes the subsystem easier to use. 
+
+### When to use
+
+* you want to provide a simple interface to a complex subsystem
+* there are many dependencies between clients and the implementation classes of an abstraction
+* you want to layer your subsystems, use a facade to define an entry point to each subsystem level 
+ 

flyweight/README.md

@@ -0,0 +1,12 @@
+## Flyweight
+
+Use sharing to support large numbers of fine-grained objects efficiently. 
+
+### When to use
+
+* when all of the following are true
+ * an application uses a large number of objects
+ * storage costs are high because of the sheer quantity of objects
+ * most object state can be made extrinsic
+ * many groups of objects may be replaced by relatively few shared objects once extrinsic state is removed
+ * the application doesn't depend on object identity 

proxy/README.md

@@ -0,0 +1,7 @@
+## Proxy
+
+Provide a surrogate or placeholder for another object to control access to it. 
+
+### When to use
+
+* whenever there is a need for a more versatile or sophisticated reference to an object than a simple pointer