Multiplication of two ints overflowing to result in a negative number

Question

Consider this snippet from the Java language specification.

class Test {
    public static void main(String[] args) {
        int i = 1000000;
        System         


        

Answer 1

The reasons why integer overflow occurs have already been explained in other answers.

A practical way to ensure long arithmetic in calculations is to use numeric literals with l suffix that declare the literals as long.

Ordinary integer multiplication that overflows:

jshell> 100000 * 100000
$1 ==> -727379968

Multiplication where one of the multiplicands has l suffix that does not overflow:

jshell> 100000 * 100000l
$1 ==> 1000000000000

Note that longs are also prone to overflow, but the range is much greater, from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807.