According to the API docs (our friend)
public static int abs(int a)
Returns the absolute value of an int value. If the argument is not negative, the argument is returned. If the argument is negative, the negation of the argument is returned.
Note that if the argument is equal to the value of Integer.MIN_VALUE, the most negative representable int value, the result is that same value, which is negative.
Parameters:
a - the argument whose absolute value is to be determined
Returns:
the absolute value of the argument.
The absolute value of Integer.MIN_VALUE can not represented as a positive value as a
Java int.