CODEWITHSUNDEEP
javaloopsfor-loop
user3630501
user3630501

Reputation: 71

Atypical loop output

For the loop

int r = 10;
for(int h=0;h<r;h--)
{
    r--;
}
out.print(r);

the output is -2147483639. I'm not sure why the loop wouldn't be infinitely repeating, and I can't quite figure out the significance of the outputted number (besides the fact that it is near the int MIN_VALUE). What exactly is happening?

Upvotes: 0

Views: 42

Answers (2)

Elliott Frisch
Elliott Frisch

Reputation: 201429

In addition to overflow, there is arithmetic underflow. In your case, the value of h underflows before r (at which point, it is Integer.MAX_VALUE) and thus h is greater than r and the loop ends.

int r = Integer.MIN_VALUE;
System.out.println(r);
r--;
System.out.println(r);

Output is

-2147483648
2147483647

Upvotes: 1

Andreas
Andreas

Reputation: 159086

r,h starts out 10,0, then each iteration counts down both by 1, e.g. 9,-1, 8,-2, and on.

Eventually, h reaches Integer.MIN_VALUE, i.e. r=-2147483638, h=-2147483648, before it underflows the int and becomes r=-2147483639, h=2147483647, at which point h<r becomes false, and the loop ends.

Result: -2147483639

Note: If you change int to long, the underflow will still happen, it'll just take a heck of a lot longer.

Upvotes: 1

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