Introduction to Java Class Diagrams

Introduction to Java Class Diagrams

Classes class Account { … } Account

Attributes class Account { float balance = 0; float limit; } Account balance: float = 0 limit: float [visibility] attributeName [multiplicity] [: type [ = initialValue ] ]

Visibility class Account { private float balance = 0; private float limit; } Account - balance: float = 0 - limit: float • + public • private • # protected • ~ package

Operations (methods) class Account { private float balance = 0; private float limit; public void deposit(float amount) public void withdraw(float amount) } Account - balance: float = 0 - limit: float + deposit( amount: float ) + withdraw( amount: float ) [visibility] methodName( [parameter: type]* ) [ : returnType]

Class scope class Person { private static int numPeople; private String name; public String getName() public static int getNumPeople() } Person - numPeople: int - name: String + getName() : String + getNumPeople() : int

CompositionA comprises local objects that die when A dies class Basket { Item item = new Item(); } Basket Item

Aggregationcomprised of sharable objects class Computer { Device dev; Computer(Device dev) { this.dev = dev; } } Computer Device

Multiplicities class Basket { Item item = new Item(); } 1 Basket Item

Multiplicities class Basket { Item[] item = new Item[5]; } 5 Basket Item

Multiplicities class Basket { // may or may not exist Item item; } 0..1 Basket Item i..j means i <= # objects <= j

Multiplicities class Basket { List<Item> itemList = newArrayList<Item>(); } 0..* Basket Item * means no a priori upper limit

Generalization (is a) Person class Person { … } class Employee extends Person { … } Employee

Realization interface Person { … } class Employee implements Person { … } Person Employee Person Employee

Introduction to Java Class Diagrams