Varargs methods and primitive types

Question

In Effective Java J. Bloch mentioned that it was not safe to use varargs method with primitive types. Percisely, Arrays.asList(1, 2, 4) had return type List<int[]> and it sounds quite reasonble. Now I tried to reproduce this behaviour myself and couldn't:

My question is why is the type deduced to List<Integer> but not to List<int[]> as he stated? Does it mean, that in Java 8 the problem about varargs is not relevant anymore and we can safely use them anywhere we want if we don't care about performance too much.

score 5 · Accepted Answer · edited May 08 '16 at 17:12

5

Author most probably meant that you can't pass array of primitive type elements and expect it to be boxed like

int[] intArray = {1,2,3};
Arrays.asList(intArray);

which will return List<int[]> not List<Integer> since there is no autoboxing of arrays like int[]->Integer[] so only possible type which can be used by T... vararg is int[] since generic type T can't represent primitive type.

Other possible problem is that you are reading first edition of book (released in 2001) but autoboxing was added in Java 1.5 (Java 5.0) which was released in 2004.

edited May 08 '16 at 17:12

Pshemo

122,468
25
185
269

answered May 08 '16 at 09:47

FooBar

66
2

But varargs was added in Java 1.5 too, so if the book mentions varargs it must be Java 5+. – newacct May 09 '16 at 23:57

Varargs methods and primitive types

1 Answers1

Linked