将arraylist传递给另一个类

Question

I'm fairly new to programming and I'm a bit confused here. I am trying to pass a filled arraylist to another class. Here's the class where I make the arraylist:

public class inventory
{    
    private static ArrayList<engineSpecs> list = new ArrayList<engineSpecs>();
    public inventory()
    {        
        //Instantiates objects of constructor engineSpecs
        engineSpecs astonmartin = new engineSpecs("Aston Martin", "Vanquish", 350000, 11, "Gray",
                                     2015, 565, 457, "automatic");
        engineSpecs ferrari = new engineSpecs ("Ferrari", "458 Italia", 240000, 13, "Red", 2015, 
                                       570, 398, "automatic"); 

        //Adds objects into array list
        list.add(astonmartin);
        list.add(ferrari);   
    }
    public static ArrayList<engineSpecs> getList()
    {
        return list;
    } 
}

And here's the class I'm trying to pass the arraylist to:

public class Main
{
    public static void main (String[] args)
    {        
    inventory inventory = new inventory();
    System.out.println (inventory.getList());
    }
}

When I run the main class, it just prints out an empty arraylist. Any help is greatly appreciated!

Answer 1

By default when you print a list it will display it as follows

[ classname of element of list@HashCode ]

If you want a list to be displayed in a specific way you need to override the toString method of the class which is added to the list. In your case the enginespecs class

Adding a simple toString in engineSpecs class like below will give you a desired result

public String toString(){
return name;
}

OUTPUT

[Aston Martin, Ferrari]

NOTE

In java class names need to begin with capital. And a parameter should be declared static only if you want to use it at the class level

Answer 2

The results will not be null or empty. It will have entries as well. If you override toString for the class "engineSpecs " you can see the entries of list.

Answer 3

Try decalaring it as instance variable instead of static. and remove static way of accessing the list.