How to convert int[] into List in Java?

Question

How do I convert int[] into List in Java?

Of course, I\'m interested in any other answer than doing it in a loop, item by it

Answer 1

give a try to this class:

class PrimitiveWrapper extends AbstractList {

    private final T[] data;

    private PrimitiveWrapper(T[] data) {
        this.data = data; // you can clone this array for preventing aliasing
    }

    public static  List ofIntegers(int... data) {
        return new PrimitiveWrapper(toBoxedArray(Integer.class, data));
    }

    public static  List ofCharacters(char... data) {
        return new PrimitiveWrapper(toBoxedArray(Character.class, data));
    }

    public static  List ofDoubles(double... data) {
        return new PrimitiveWrapper(toBoxedArray(Double.class, data));
    }  

    // ditto for byte, float, boolean, long

    private static  T[] toBoxedArray(Class boxClass, Object components) {
        final int length = Array.getLength(components);
        Object res = Array.newInstance(boxClass, length);

        for (int i = 0; i < length; i++) {
            Array.set(res, i, Array.get(components, i));
        }

        return (T[]) res;
    }

    @Override
    public T get(int index) {
        return data[index];
    }

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

testcase:

List ints = PrimitiveWrapper.ofIntegers(10, 20);
List doubles = PrimitiveWrapper.ofDoubles(10, 20);
// etc