Composite pattern - Structural

• treats a group of objects in similar way as a single object
• creates a class that contains group of its own objects 
• uses tree structures to represent part-whole hierarchies
  Build a complex object out of elemental objects and itself like a tree structure

Where to use ?

• To represent a part-whole relationship like tree folder system
• When clients ignore the difference between compositions of objects and individual objects
• Used to let clients treat individual objects and compositions of objects uniformly.

Implementation example

• Class Employee containing list of staff (List of Employee objects)
  Employee class can have methods to add its staff