guava/src/com/google/common/primitives/ImmutableIntArray.java
public static ImmutableIntArray copyOf(Collection<Integer> values) {
    return values.isEmpty() ? EMPTY : new ImmutableIntArray(Ints.toArray(values));
  }
public static ImmutableIntArray copyOf(Collection<Integer> values) {
    return values.isEmpty() ? EMPTY : new ImmutableIntArray(Ints.toArray(values));
  }
Returns an immutable array containing the given values, in order.