Java的奇怪行为

Question

hello I have some question about java, why the following code return strange value?

System.out.println("Strange " + (20 * 232792560)/20);

why do I recieve 18044195 ?

Answer 1

Because (20 * 232792560) overflows the range of an int , and wraps round the number range several times to become 360883904 . That is then divided by 20 to give you the result that you see.

If you want the correct result, then you need to do:

System.out.println("Strange " + (20 * 232792560L) / 20);

(Marking a literal with an L means that the constant maths will be done with long , rather than with int , so this will no longer overflow.)

Answer 2

由于(20 * 232792560)将执行基于整数的乘法，并且结果显然超出int的范围，因此该值将被截断。

Answer 3

Because 20 * 232792560 does not fit in 4 bytes (integer value).

So you got:

20 * 232792560 = 360883904; // because of int overflow
360883904 / 20 = 18044195;