Java：指定long时L和l（小写L）有区别吗？

Question

When I specify a number to be a long with a constant value 400 , is there any difference between using 400L and 400l ?

Does it have some relationship to the wrapper type? Is L used to get a wrapper Long and l for the primitive data type long ?

Answer 1

No practical difference. Either L or l can be used, both indicate a long primitive. Also, either can be autoboxed to the corresponding Long wrapper type.

However, it is worth noting that JLS-3.10.1 - Integer Literals says (in part)

An integer literal is of type long if it is suffixed with an ASCII letter L or l (ell); otherwise it is of type int ( §4.2.1 ).

The suffix L is preferred, because the letter l (ell) is often hard to distinguish from the digit 1 (one).

Answer 2

Yes: it's readability.

It's easy to mistake 400l for four thousand and one when you first glance at it.

I find it more likely to interpret it correctly as four hundred long with the upper case L.

Answer 3

Just to add to the answers already here we can actually prove that both 400l and 400L are the primitive long using the Local Variable Type Inference.

var num = 10L;
System.out.println(num instanceof Object);

Will cause a compiler error as primitive types cannot be used with instanceof .

This is not the case with either Long num = 1L as it autoboxed or with var num = new Long(1) .

Though the latter will cause a deprecation warning in versions older than Java 9.