Difference between long a = 1 and long a = 1L

My question is long a = 1; an integer in reality? And is it the same as long a = 1L; in data type?

>Solution :

You can see from the following experiments that the literals (not prefixed with L) are ints, but that there are automatic casts such that a long variable finaly always holds a long value:

long a = 2147483647 + 1;

long b = 2147483647;
b++;

long c = 2147483647L + 1;

• For a, the literals are ints. The calclulation is done with ints, which overflows. Therefore long a gets assigned -2147483648L.
• For b, the int literal is casted to long during assignment, which can be incremented to the final value b = 2147483648L without overflow.
• For c, the calculation is already done with longs (the int literal 1 is automatically casted to 1L), giving c = 2147483648L in first place.

You can find the specification for numeric promotion in JLS 5.6 "Numeric Contexts"