In Java what do arrays inherit from? Can I do this?

Question

Sorry for the newbie question, I'm used to C# so my Java framework knowledge is not so good.

I have a couple of arrays:

int[] numbers = new int[10];
String[] names = new String[10];

//populate the arrays

Now I want to make a generic function which will print out the values in these arrays, something like the following (this should work in C#)

private void PrintAll(IEnumerable items)
{    
    foreach(object item in items)       
        Console.WriteLine(item.ToString());
} 

All I would have to do now is to

PrintAll(names);
PrintAll(numbers);

How can I do this in Java? What is the inheritance tree for the array in Java?

Many thanks

Bones

Answer 1

Arrays only implement Serializable and Cloneable in Java¹; so there is no generic way to do this. You'd have to implement a separate method for each type of array (since primitive arrays like int[] cannot be cast to Object[]).

But in this case, you don't have to because Arrays can do it for you:

System.out.println(Arrays.toString(names));
System.out.println(Arrays.toString(numbers));

This will yield something like:

[Tom, Dick, Harry]
[1, 2, 3, 4]

If that's not good enough, you're stuck having to implement a version of your method for each possible array type, like Arrays does.

public static void printAll(Object[] items) {
    for (Object o : items)
        System.out.println(o);
}
public static void printAll(int[] items) {
    for (int i : items)
        System.out.println(i);
}
public static void printAll(double[] items) {
    for (double d : items)
        System.out.println(d);
}
// ...

Note that the above only applies to arrays. Collection implements Iterable, so you can use:

public static <T> void printAll(Iterable<T> items) {
    for (T t : items)
        System.out.println(t);
}

¹ See JLS §10.7 Array Members.