How do I clear up this ambiguous call to Arrays.copyof()?

Question

I'm running AIDE on my Android phone, and am having trouble compiling the following bit of Java code:

elements = Arrays.copyOf(elements, elements.length * 2);

Here elements is of type int[]. The error I'm getting from AIDE is

Several methods are applicable to (int[], int): 'java.util.Arrays.copyOf(int[], int)' and 'java.util.Arrays.copyOf<T>(T[], int)'

I would've expected the compiler to pick the former option, but it doesn't. How can I resolve this?

Sounds like a compiler/IDE problem, because there's really just one valid overload that could be used (the first one). Plus: Eclipse can easily compile this line and knows exactly which one to call. — Joachim Sauer, Sep 17 '12 at 10:49
It must be a compiler problem if it works in eclipse then. Still, anyone know if there a way to coax the compiler into picking one? — Hannesh, Sep 17 '12 at 10:55
Just wondering - why aren't you using an `ArrayList` as that would handle the resizing for you. — David Webb, Sep 17 '12 at 11:08
Have you tried casting the first argument to int[]: `Arrays.copyOf((int[]) elements, elements.length * 2)`? — JB Nizet, Sep 17 '12 at 11:12
@Dave, because ArrayList boxes each value, which has a pretty big overhead. — Hannesh, Sep 17 '12 at 11:21
Sounds like a bug for me. I just tried this IDE, static imports seems not to work either. And there not hint about which compiler is used. Iwould suggest to raise a bug or switch to another android IDE — cporte, Sep 17 '12 at 12:32

gexicide · Accepted Answer · 2012-09-18T08:42:19.497

1

This is a compiler/IDE problem. However, Arrays.copyOf is a quite trivial function, so simply write your own version of it if the problem can't be fixed with IDE/compiler updates. Another way would be to use reflection to call it. But it comes with some runtime overhead and also makes the code look awkward, so I suggest implementing your own version.

Here is the code:

public static int[] copyOf(int[] original, int newLength) {
    int[] copy = new int[newLength];
    System.arraycopy(original, 0, copy, 0,
                     Math.min(original.length, newLength));
    return copy;
}

Of course, if you then get the same problem for System.arraycopy, then this does not work. Simply try it. If it does not work, you can place it in a helper class and use a non-buggy compiler to compile this helper class.

edited Sep 18 '12 at 08:42

answered Sep 18 '12 at 08:36

gexicide

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@JoachimSauer: Not true. `Arrays.copyOf` is a normal java function that just creates a new array and invokes `System.arrayCopy`. Added its source code to the answer. – gexicide Sep 18 '12 at 08:39
indeed, I confused it with `System.arraycopy`. – Joachim Sauer Sep 18 '12 at 08:45
Yes it must be a compiler problem. I'll submit a bug report – Hannesh Sep 19 '12 at 14:19

How do I clear up this ambiguous call to Arrays.copyof()?

1 Answers1