Converting Integer to Long

Question

I need to get the value of a field using reflection. It so happens that I am not always sure what the datatype of the field is. For that, and to avoid some code duplication

Answer 1

This is null-safe

Number tmp = getValueByReflection(inv.var1(), classUnderTest, runtimeInstance);
Long value1 = tmp == null ? null : tmp.longValue();

Answer 2

In case of a List of type Long, Adding L to end of each Integer value

List<Long> list = new ArrayList<Long>();
list  = Arrays.asList(1L, 2L, 3L, 4L);

Answer 3

new Long(Integer.longValue());

or

new Long(Integer.toString());

Answer 4

If you don't know the exact class of your number (Integer, Long, Double, whatever), you can cast to Number and get your long value from it:

Object num = new Integer(6);
Long longValue = ((Number) num).longValue();