Java Generics Programming with Collection

I have being stuck with this assignment for weeks now. I just need some help for starting. Here is first requriment:

Design a generic container called GenericOrder that acts as a collection of an arbitrary number of objects in Product开发者_StackOverflow社区s.java. Design a mechanism that gives each instance of the container a unique identifier. Implement as many methods as necessary. You must use Java generics features.

Here is what I have, I don't if I did right or not. The instructor says, this GenericOrder must use collection to hold multiple "Product".

public class GenericOrder<T> {
    private T theProduct;
    private static int count = 1;
    private final int orderNumber = count++;
    private Collection<T> genCollection;

    public GenericOrder(T theClass)
    {
        this.theProduct = theClass;
    }

    public String getProductID()
    {
     return theProduct.getClass().getName() + ": " + orderNumber;
    }

    public T createInstance()
    throws IllegalAccessException, InstantiationException {
        return this.theProduct;
    }
}

I would imagine there can be multiple "products" per "order":

public class GenericOrder<T> {
  List<T> productsOrdered ...
  public GenericOrder(List<T> products) {
     ...
  }
}

But I really have no idea how generics are supposed to help with that, and I can't honestly "piece together" the assignment from just that context so, YMMV.

Happy coding. :)

Design a generic container called GenericOrder that acts as a collection of an arbitrary number of objects

Rather change your container to include what @pst suggested.

Design a mechanism that gives each instance of the container a unique identifier.

Here you got it almost right. But your general thinking was correct.

public class GenericOrder<T> {
    private static int ID = 0;
    private String serial;
    List<T> products;

    public GenericOrder() {
        serial = "CONTAINER_" + ID++;
        products = new ArrayList<T>();
    }

    public String getUniqueSerial() {
        return serial;
    }

    public void addProduct(T newProduct) {
        products.add(newProduct);
    }

    public int getNumberOfProducts() {
        return products.size();
    }
}

I might be all wrong here, but it sounds to me like you should inherit from Collection. And for the unique identifier I would perhaps use a map.