Introduction

Fundamental Principles

• clarity and simplicity
• the user of a component should never be surprised by its behaviour
• components should be as small as possible but no smaller
• code reuse > code copying
• minimal dependencies between components
• errors detected ASAP
  • ideally at compile time

• principles can be violated occasionally within good reason
• clear, correct, usable, robust, flexible, maintainable code > performance

Terminology

• Types
  • 4 Types
    1. Interfaces (includes annotations)
    2. Classes (includes enums)
    3. Arrays
    4. Primitives
  • Interfaces, classes and arrays are known as reference types
    • primitives are known as value types
  • objects are class instances and arrays
  • A class’ members
    • fields
    • methods
    • member classes
    • member interfaces
  • A method’s signature - name - types of formal parameters - does NOT include the method’s return type
• A class implements an interface.
• An interface extends another.
• package access $\rightarrow$ package-private
• (exported) API refers to classes, interfaces, constructors, members and serialized forms (API elements) by which a programmer accesses a class, interface or package
  • API = Applicable Programming Interface
  • A class whose implementation uses an API is a client of the API
  • exported = accessible outside of the package that defines the API