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UML.md

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Primitives and Objects

Primitives

  • int 4 bytes
  • char 2 bytes
  • long 8 bytes
  • float 4 bytes
  • double 8 bytes
  • Boolean 1 byte (smallest amount of data allowed to stored in memory)

Objects

  • String
  • Integer

Difference between primitives and objects (In Java)

  • Objects automatically choose the length of storage.
  • Objects have methods to be called.

Relationship between classes and UML diagrams

Relationships

  • Association

A line.

  • Generalization / inheritance

An solid line with triangular arrow.

  • Implimentation (from a interface)

Dotted lined with triangular arrow.

  • Dependence

Dotted line with acute arrow.

Goals for UML diagram: Minimize dependencies

More dependence means more complexity; more complexity means more possible errors generated from other classes. It also means more difficulty to maintain.

To reduce dependency:

  • Encapsulation (Information hiding)

To decrease the dependency through classes.

  • Modularity

Modularity is dividng each levels of design into separatable parts. It's a kind of abstraction.

To decrease the dependency through modules.

  • Encapsulation and Modularity creates interfaces between programs that information can only be transmitted through.

Notes:

  • This is UML class diagram, so there is no instantiation in it.