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

Try to convertValue by Jackson

ObjectMapper mapper = new ObjectMapper()
Integer a = 1;
Long b = mapper.convertValue(a, Long.class)

Answer 2

Oddly enough I found that if you parse from a string it works.

 int i = 0;
 Long l = Long.parseLong(String.valueOf(i));
 int back = Integer.parseInt(String.valueOf(l));

Win.

Answer 3

Use the following: Long.valueOf(int);

or (Long) int ;

Answer 4

Integer i = 5; //example

Long l = Long.valueOf(i.longValue());

This avoids the performance hit of converting to a String. The longValue() method in Integer is just a cast of the int value. The Long.valueOf() method gives the vm a chance to use a cached value.

Answer 5

If the Integer is not null

Integer i;
Long long = Long.valueOf(i);

i will be automatically typecast to a long.

Using valueOf instead of new allows caching of this value (if its small) by the compiler or JVM , resulting in faster code.

Answer 6

Convert an integer directly to long by adding 'L' to the end of Integer.

Long i = 1234L;