CODEWITHSUNDEEP
javaarrayslistarraylist
kamikaze_pilot
kamikaze_pilot

Reputation: 14834

Why does Arrays.asList on an int[] return a List<int[]>, and not a List<int>?

Consider this code:

int[] tcc = {1,2,3};
ArrayList<Integer> tc = Arrays.asList(tcc);

For the above, Java complains that it cannot convert from List<int[]> to ArrayList<Integer>.

What's wrong with this?

Why is it List<int[]> and not List<int>?

Upvotes: 3

Views: 395

Answers (3)

Zach L
Zach L

Reputation: 16262

You could have it as:

List<int[]> tc = Arrays.asList(tcc);

Arrays.asList returns a List, not an ArrayList. And since Arrays.asList is a varargs function, it thinks tcc is one element of a bigger array.

If you want to have just a List of Integers, you'd have to rewrite it as SB mentioned in the comments for Hovercraft Of Eel's answer:

List<Integer> tc = Arrays.asList(1, 2, 3);

Alternatively, if you make tcc an Integer[], you can still use your array as an argument in the following snippet by explicitly asking for a List of Integer, providing a type parameter that agrees with the passed array:

 Integer[] tcc = {1,2,3};
 List<Integer> tc = Arrays.<Integer>asList(tcc);

Upvotes: 1

Kaffiene
Kaffiene

Reputation: 713

This will work:

ArrayList tc = new ArrayList(Arrays.asList(1,2,3));

Upvotes: 1

Hovercraft Full Of Eels
Hovercraft Full Of Eels

Reputation: 285403

An ArrayList can hold only objects not primitives such as ints, and since int != Integer you can't do what you're trying to do with an array of primitives, simple as that. This will work for an array of Integer though.

Upvotes: 3

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