Idiom for container classes

Question

I was told to design the code according to the following code example:

Class Dogs{
   List<Dog> listOfDogs = new ArrayList<Dog>();
   // Setters, getters...
}

Class Dog{
   // Attributes and methods
}

The question arises: why is it better to implement the class Dogsas a container for ArrayList objects Dog, and not just refer to a simple ArrayList. Is encapsulation considered?

Answer 1

Basically, creating a class Dogsprovides you with an extra layer of indirection.

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Answer 2

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List listOfDogs = new ArrayList<Dog>();

:

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, : :

List<Dog> listOfDogs = new ArrayList<Dog>();

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Answer 3

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Class Dogs
{
  List listofDogs = new ArrayList<Dog>();

  public void AddDog(Dog newDog)
  {
     //check if valid
  }

  public List<Dog> getDogs()
  {
    //return readonly dogs collection
  }
}

Answer 4

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Answer 5

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Answer 6

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Answer 7

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