assert - assertion compareTo in java -

assert - assertion compareTo in java -

string title ="a"; int year = 2009; string director = "zebra"; string title1 ="b"; int year1 = 2010; string director1 = "zzz"; videoobj = new videoobj(title,year,director); videoobj b = new videoobj(title2,year,director); assert.asserttrue( a.compareto(b) == -b.compareto(a) );

what meaning of - in assert.asserttrue( a.compareto(b) == -b.compareto(a) ); statement???

please can explanation?

thanks

the meaning of - negation, plain , simple. i've seen idiom in numeric comparisons homecoming -1, 0 or +1 value, depending on comparison. although work homecoming magnitude well, -n, 0, +n (where n identical).

it's checking compareto operations give opposite value when reverse operands. in other words, it's assertion compareto functions expected (but not guaranteed - see below).

if a < b , b < a (ie, a both less than, and greater b), have serious problem needs fixing :-)

from compareto documentation:

the implementor must ensure sgn(x.compareto(y)) == -sgn(y.compareto(x)) x , y.

in foregoing description, notation sgn(expression) designates mathematical signum function, defined homecoming 1 of -1, 0, or 1 according whether value of look negative, 0 or positive.

based on that, assertion not quite right, should comparing integer.signum (a.compareto (b)) rather a.compareto (b), unless has knowledge implementation of compareto guaranteed homecoming symmetrical (around zero) values.

java assert