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From: Tom Anderson on 23 Jul 2010 14:17
On Thu, 22 Jul 2010, Simone wrote:

> I also noticed that the solution with Arrays.asList(vector) works only
> if vector is an array of a wrapper class and not if it's an array of a
> primitive type, in which case the output is, again, the hash code of the
> array.

Aah, ya gots me.

Yes, in this case, you are largely stuffed. UNLESS you pay heed to my
super-wily suggestion:

public class ArrayWrapper extends AbstractList{
private Object[] array;

public ArrayWrapper(Object[] array) {
this.array = array;
}

@Override
public Object get(int index) {
Object object = array[index];
if (object instanceof Object[]) object = new ArrayWrapper((Object[]) object);
return object;
}

@Override
public int size() {
return array.length;
}
}

Try:

System.out.println(new ArrayWrapper(new Object[][] {{1, 2, 3}, {'a', 'b', 'c'}, {true, false, true}}));

This only works with arrays of objects, but you could write a family of
specialised versions for arrays of primitives, and create the appropriate
one in the getter.

> On 19 Lug, 13:53, Tom Anderson <t...(a)urchin.earth.li> wrote:
>> On Mon, 19 Jul 2010, Simone wrote:
>>> Is there a way to rewrite the "implicit" toString() method for arrays,
>>> so that I can write System.out.println( "v =" + vector ) and obtain the
>>> output: v = (1,2,3,4) ?
>>
>> Sadly not.
>>
>> The best sticking-plaster is usually to wrap the array in a list:
>>
>> System.out.println(Arrays.asList(vector));
>>
>> That method returns a lightweight wrapper around the array that, amongst
>> other things, implements a more sensible toString.

--
I drink quarts and cans and bottles and sixes; between the turntables
keep the vodka and the mixes. -- MCA
From: markspace on 23 Jul 2010 14:45
Tom Anderson wrote:

> Yes, in this case, you are largely stuffed. UNLESS you pay heed to my
> super-wily suggestion:
....
> This only works with arrays of objects, but you could write a family of
> specialised versions for arrays of primitives, and create the
> appropriate one in the getter.


I thought my autoBox() method was more wily, because it dealt with
primitives. But what the hay, more ideas is mo' bettah.
From: Tom Anderson on 25 Jul 2010 12:09
On Fri, 23 Jul 2010, markspace wrote:

> Tom Anderson wrote:
>
>> Yes, in this case, you are largely stuffed. UNLESS you pay heed to my
>> super-wily suggestion:
> ...
>> This only works with arrays of objects, but you could write a family of
>> specialised versions for arrays of primitives, and create the appropriate
>> one in the getter.
>
> I thought my autoBox() method was more wily, because it dealt with
> primitives.

You deal with primitives, but not nested lists, which is where i was
applying wiliness. We are disjointly wily. But we can unionise: in my
wrapper, change the type of the array instance variable to Object, and
rewrite the getter to use your reflective approach:

Object object = Array.get(array, index);
if (obj.getClass().isArray()) object = new ArrayWrapper(object);
return object;

Now we have something that handles primitives and nested lists, and does
so with minimal allocation (just small wrapper objects, never arrays), and
doesn't require a type parameter to be passed in.

It's not as generally useful as your unbox method could be, because it
isn't typesafe, but it will do for toString.

tom

--
Pool's closed.
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