Geek asks and answers

UML class diagram structure with class hierarchies

I was wondering if I could model the relationship between the two class hierarchies below, the way I did it:

car-engine composition relationship

The code that will represent the meaning of this will be something like this:

public abstract class Car
{
    protected Engine engine;  
}
public class StreetCar extends Car
{
     public StreetCar()
     {
          engine = new StreetEngine();
     }
}

... and similarly for the OffroadCar class, it will do something like engine = new OffroadEngine(). I did not add anything about the acceleration method (), this is not relevant.

I just want to know if the composition is modeled correctly or if it is redundant or even incorrect to add many composition arrows.

+5
source share
1 answer

Before answering the question, this is one of those cases where it is a good idea to separate hierarchical relations from compositional relations, as if they had different types of diagrams.

. Engine "" "Class", .

(1)

"CarClass" "EngineClass".

..............................................................................
..+-------------------------------------+........+-------------------------+..
..|           <<abstract>>              |........|      <<abstract>>       |..
..|             CarClass                |........|       EngineClass       |..
..+-------------------------------------+........+-------------------------+..
..| [#] Engine: EngineClass             |<*>-----+ [+] startEngine(): void |..
..+-------------------------------------+........+-------------------------+..
..| [+] acelerate(): void <<virtual>>   |.....................................
..+-------------------------------------+.....................................
..............................................................................

(2.1)

"CarClass" .

...........................................
..+-------------------------------------+..
..|           <<abstract>>              |..
..|             CarClass                |..
..+-------------------------------------+..
..| [#] Engine: EngineClass             |..
..+-------------------------------------+..
..| [+] acelerate(): void <<override>>  |..
..+-----------------+-------------------+..
.................../.\.....................
................../...\....................
.................+--+--+..............................................................
....................|.................................................................
....................+------------------------------------------+......................
....................|..........................................|......................
..+-----------------+-------------------+....+-----------------+-------------------+..
..|           <<concrete>>              |....|           <<concrete>>              |..
..|            StreetCarClass           |....|           OffRoadCarClass           |..
..+-------------------------------------+....+-------------------------------------+..
..| [+] acelerate(): void <<override>>  |....| [+] acelerate(): void <<override>>  |..
..+-------------------------------------+....+-------------------------------------+..
......................................................................................

(2.2)

"EngineClass" .

...........................................
..+-------------------------------------+..
..|           <<abstract>>              |..
..|             EngineClass             |..
..+-------------------------------------+..
..| [+] acelerate(): void <<override>>  |..
..+-----------------+-------------------+..
.................../.\.....................
................../...\....................
.................+--+--+..............................................................
....................+------------------------------------------+......................
....................|..........................................|......................
....................|..........................................|......................
..+-----------------+-------------------+....+-----------------+-------------------+..
..|           <<concrete>>              |....|           <<concrete>>              |..
..|          StreetEngineClass          |....|          OffRoadEngineClass         |..
..+-------------------------------------+....+-------------------------------------+..
..| [+] startEngine(): void <<override>>|....| [+] startEngine(): void<<override>> |..
..+-------------------------------------+....+-------------------------------------+..
......................................................................................

3

, , , , . " Paralell" " ".

2 , .

. -, , , , .

3.1.

..............................................................................
..+-------------------------------------+........+-------------------------+..
..|           <<abstract>>              |........|       <<abstract>>      |..
..|             CarClass                |........|        EngineClass      |..
..+-------------------------------------+........+-------------------------+..
..| [#] Engine: EngineClass             |<*>-----+ [+] startEngine(): void |..
..+-------------------------------------+........+------------+------------+..
..| [+] acelerate(): void <<virtual>>   |.....................|...............
..+--------------+----------------------+.....................|...............
.................|............................................|...............
.................+--------------------------------------------+...............
.................|............................................................
........+--------+-------+....................................................
........|   Note:        |....................................................
........|   Paralell     /....................................................
........|   Hierarchy   /| ...................................................
........|              / |....................................................
........+-------------/--+....................................................
..............................................................................

, , .

3.2

..............................................................................
..+---------------------------------------+........+-------------------------+..
..|             <<concrete>>              |........|       <<concrete>>      |..
..|            OffRoadCarClass            |........|    OffRoadEngineClass   |..
..+---------------------------------------+........+-------------------------+..
..| [+] createEngine(): void <<override>> |<*>-----+ [+] startEngine(): void |..
..+---------------------------------------+........| [+] nitroLevel(): void  |..
..| [+] useNitro(): void                  |........+------------+------------+..
..| [+] acelerate(): void <<override>>    |.....................|...............
..+--------------+------------------------+.....................|...............
.................|..............................................|...............
.................+----------------------------------------------+...............
.................|............................................................
........+--------+-------+....................................................
........|   Note:        |....................................................
........|   Paralell     /....................................................
........|   Hierarchy   /| ...................................................
........|              / |....................................................
........+-------------/--+....................................................
..............................................................................

, .

4

"" , , , overriden.

public abstract class EngineClass
{
    public void startEngine() { ... }  
} // EngineClass

public abstract class CarClass
{
    protected EngineClass engine;  

    public CarClass()
    {
      // ...
    }

    public EngineClass createEngine()
    {
      EngineClass Result = new EngineClass();
      return Result;
    }

    public void start()
    {
      this.Engine = createEngine();
    }
} // CarClass

public class StreetCarClass extends CarClass
{
     public StreetCarClass()
     {
       // ...
     }

    @override
    public EngineClass createEngine()
    {
      EngineClass Result = new StreetCarEngineClass();
      return Result;
    }
} // StreetCarClass 

public class OffRoadCarClass extends CarClass
{
     public OffRoadCarClass()
     {
       // ...
     }

    @override
    public EngineClass createEngine()
    {
      EngineClass Result = new OffRoadCarEngineClass();
      return Result;
    }
} // OffRoadCarClass 

public class ExampleClass
{
    public static main()
    {
      EngineClass OffRoadCar = new OffRoadCarClass();
      OffRoadCar.start();
    }
} // OffRoadCarClass

.

P.S. , , ?

+3

More articles:


All Articles