Java autoboxing and unboxing

I am trying to convert and array ints to a List however every time I try I get a compilation error. 

   List<Integer> integers = toList(draw.getToto6From49().getFirstRound());

// getFirstRound() returns int[] ;

and here is my to toList method 

public class ArraysUtil {


 public static <T> List<T> toList(T[] ts) {
  List<T> ts1 = new ArrayList<>();
  Collections.addAll(ts1, ts);
  return ts1;
 }
}

java: method toList in class com.totoplay.util.ArraysUtil cannot be applied to given types;

  required: T[]
  found: int[]
  reason: inferred type does not conform to declared bound(s)
    inferred: int
    bound(s): java.lang.Object
Jon Skeet
people
quotationmark

Yes, you can't do that, basically. You're expecting to be able to call toList with a type argument of int, and Java doesn't allow primitives to be used as type arguments. You basically need a different method for each primitive you want to handle like this, e.g.

public static List<Integer> toList(int[] ts) {
  List<Integer> list = new ArrayList<>(ts.length);
  for (int i in ts) {
    list.add(i);
  }
}

At least, that's the case in Java 7 and before. In Java 8 it's slightly simpler:

int[] array = { 1, 2, 3 };
IntStream stream = Arrays.stream(array);
List<Integer> list = stream.boxed().collect(Collectors.toList());

people

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