docs: update Composite docs

composite/README.md

@@ -4,8 +4,15 @@ category: Structural
 language: en
 tag:
     - Gang of Four
+    - Object composition
+    - Recursion
 ---
 
+## Also known as
+
+* Object Tree
+* Composite Structure
+
 ## Intent
 
 Compose objects into tree structures to represent part-whole hierarchies. Composite lets clients
@@ -183,11 +190,39 @@ individual objects. Clients will treat all objects in the composite structure un
 
 ## Known uses
 
-* [java.awt.Container](http://docs.oracle.com/javase/8/docs/api/java/awt/Container.html) and [java.awt.Component](http://docs.oracle.com/javase/8/docs/api/java/awt/Component.html)
+* Graphical user interfaces where components can contain other components (e.g., panels containing buttons, labels,
-* [Apache Wicket](https://github.com/apache/wicket) component tree, see [Component](https://github.com/apache/wicket/blob/91e154702ab1ff3481ef6cbb04c6044814b7e130/wicket-core/src/main/java/org/apache/wicket/Component.java) and [MarkupContainer](https://github.com/apache/wicket/blob/b60ec64d0b50a611a9549809c9ab216f0ffa3ae3/wicket-core/src/main/java/org/apache/wicket/MarkupContainer.java)
+  other panels).
+* File system representations where directories can contain files and other directories.
+* Organizational structures where a department can contain sub-departments and employees.
+* [java.awt.Container](http://docs.oracle.com/javase/8/docs/api/java/awt/Container.html)
+  and [java.awt.Component](http://docs.oracle.com/javase/8/docs/api/java/awt/Component.html)
+* [Apache Wicket](https://github.com/apache/wicket) component tree,
+  see [Component](https://github.com/apache/wicket/blob/91e154702ab1ff3481ef6cbb04c6044814b7e130/wicket-core/src/main/java/org/apache/wicket/Component.java)
+  and [MarkupContainer](https://github.com/apache/wicket/blob/b60ec64d0b50a611a9549809c9ab216f0ffa3ae3/wicket-core/src/main/java/org/apache/wicket/MarkupContainer.java)
+
+## Consequences
+
+Benefits:
+
+* Simplifies client code, as it can treat composite structures and individual objects uniformly.
+* Makes it easier to add new kinds of components, as existing code doesn't need to be changed.
+
+Trade-offs:
+
+* Can make the design overly general. It might be difficult to restrict the components of a composite.
+* Can make it harder to restrict the types of components in a composite.
+
+## Related Patterns
+
+* [Flyweight](https://java-design-patterns.com/patterns/flyweight/): Composite can use Flyweight to share component
+  instances among several composites.
+* [Iterator](https://java-design-patterns.com/patterns/iterator/): Can be used to traverse Composite structures.
+* [Visitor](https://java-design-patterns.com/patterns/visitor/): Can apply an operation over a Composite structure.
 
 ## Credits
 
 * [Design Patterns: Elements of Reusable Object-Oriented Software](https://www.amazon.com/gp/product/0201633612/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0201633612&linkCode=as2&tag=javadesignpat-20&linkId=675d49790ce11db99d90bde47f1aeb59)
 * [Head First Design Patterns: A Brain-Friendly Guide](https://www.amazon.com/gp/product/0596007124/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0596007124&linkCode=as2&tag=javadesignpat-20&linkId=6b8b6eea86021af6c8e3cd3fc382cb5b)
 * [Refactoring to Patterns](https://www.amazon.com/gp/product/0321213351/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0321213351&linkCode=as2&tag=javadesignpat-20&linkId=2a76fcb387234bc71b1c61150b3cc3a7)
+* [Pattern-Oriented Software Architecture, Volume 1: A System of Patterns](https://amzn.to/3xoLAmi)
+* [Patterns of Enterprise Application Architecture](https://amzn.to/3vBKXWb)