The best way to transform int[] to List<Integer> in Java?
Possible Duplicate:
How to create ArrayList (ArrayList<T>) from array (T[]) in Java
How to implement this method:
List<Integer> toList(int[] integers) {
???
//return Arrays.asList(integers); doesn't work
}
There's probably a built-in method to do it somewhere* (as you note, Arrays.asList won't work as it expects an Integer[] rather than an int[] ).
I don't know the Java libraries well enough to tell you where that is. But writing your own is quite simple:
public static List<Integer> createList(int[] array) {
List<Integer> list = new ArrayList<Integer>(array.length);
for (int i = 0; i < array.length; ++i) {
list.add(array[i]);
}
return list;
}
Obviously one downside of this is that you can't do it generically. You'll have to write a separate createList method for each autoboxed primitive type you want.
*And if there isn't, I really wonder why not.
List<Integer> asList(final int[] integers) {
return new AbstractList<Integer>() {
public Integer get(int index) {
return integers[index];
}
public int size() {
return integers.length;
}
};
}
List<Integer> toList(int[] integers) {
// Initialize result's size to length of the incoming array
// this way it will not require reallocations
ArrayList<Integer> result = new ArrayList<Integer>( integers.length );
for ( int cur: integers )
{
result.add( Integer.valueOf( cur ) );
}
return result;
}
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