Question

I am trying to understand how Generics work and I have this piece of code to display the entries of newDetails a class with these kind of parameters Map. This is my code.

public class Map<Key,Value> {

    private Map<Key, Value> entry;

    public Map(){
        entry = new HashMap<Key,Value>();
    }

    public void putEntry(Key k, Value id){
        entry.put(k, id);
    }

    public void printMe(){
        System.out.println();
        for (Map.Entry<Key, Value> x: entry.entrySet()){
            System.out.print(x+" ");
        }
    }
}

Chocolates Class

    public class Chocolates<T> {

    private List<T> listOfChocolate = new ArrayList<T>(); 

    public Chocolates(T choc){
        listOfChocolate.add(choc);
    }

    public void addChocolate(T getChoc){
        listOfChocolate.add(getChoc);
    }

    public List<T> getLists(){
        return listOfChocolate;
    }
}

Main method

public static void main(String[] arg){

        Map<Chocolates<String>, Integer> newDetails = new Map<Chocolates<String>, Integer>();
        Chocolates<String> choco = new Chocolates<String>();

        newDetails.putEntry((new Chocolates<String>("Cadbury")), 1);
        newDetails.putEntry((new Chocolates<String>("Hersheys")), 2);
        newDetails.printMe();
    }

Whenever I try to ran the program it just display this one

generics.Chocolates@9931f5=1 generics.Chocolates@19ee1ac=2 

How do I display the actual entries like Cadbury 1 then Hersheys 2?

Also is there any way I can improve the main method or some parts of the program because I always create a new object whenever I add a new entry. Originally what I wanted to do is create a Generics version of this code:

Map<List<String>, Integer> newDetails = new HashMap<List<String>, Integer>();

As someone told me that its alot better to implement that line of code in a Generics Class. Any suggestions? Thanks

EDIT 2

I edited Maps Class printMe Method as Nambari have requested

public void printMe(){
        System.out.println();
        for (Map.Entry<Key, Value> x: entry.entrySet()){
            System.out.print(x.getKey()+" "+x.getValue());
        }
    }

The output is:

generics.Chocolates@9931f5 1generics.Chocolates@19ee1ac 2

But if I add this line as suggested by Joao

public String toString(){
        return listOfChocolate.toString();
    }

output is :

[Hersheys] 2[Cadbury] 1

Thanks everyone for your help!

Answer 1

Override Object#toString in the Chocolate class:

public class Chocolates<T> {

  // ...

  @Override
  public String toString() {
    return listOfChocolate.toString();
  }
}