Declaring an Long

You do not need it. It will compile just fine.

In Java the literal "1000" is an integer so this line of code:

long number = 1000;

Select allOpen in new window

is really the same as:

int constant = 1000 ;
long number = constant;

Select allOpen in new window

which still compiles (as girionis pointed out) because you can convert an integer to a long.

But if you want to create a constant which is itself a long, you need to let Java know by adding the L at the end:

long constant = 1000L ; // The right hand side is now a long
long number = constant;

Select allOpen in new window

Strictly speaking the number 1000 is a short, an integer and a long, since it falls within the range of all these three data types. You can represent 1000 with 16, 32 and 64 bits. Therefore all of them are valid:

short a = 1000;
int b = 1000;
long c = 1000;

Select allOpen in new window

But you cannot do

byte d = 1000;

Select allOpen in new window

since byte only allows positive values up to 127.