Using modulus on a double

Question

I am trying to add up the even numbers and the odd numbers separately from a given array and for some reason I get a 0 as the output for the sum of even numbers and all the values seems to be only added to the sum of odd numbers. I thought that if the digits are correct then it would work normally just as using integer values. If anyone can help me figure out how to fix this I would really appreciate it. Thank you

    double[] list2 = {-0.6179074665219488, 0.012080423982449795, -0.21346000509541063, 0.08299652983289585, 2.44401680106775, 4.902778859313734, 1.7132831483350532, -4.2004763396051725, -4.043856195861675, -2.6728507023602326, 5.181911533071974, -2.1235877432845354, 7.603895698367564, -5.6730748575837975, -3.5868701412258464, 8.50824673494424, 1.9530312960520657, 1.4057711751329447, -6.6010520166956885, -0.8889270825881894, -3.066437913144831, -1.047977711607209, -0.6183425325427638, -1.9567474971238643, -1.6108985491087715, -3.4762343504063105, -0.7819967483948718, 1.2787199500848474, -1.724036624119682, 4.134045084705252, -4.302090407212001, 4.522452909896921, -9.510982189042458, 4.483571903648103, 4.734972592935479, 1.3007048393668028, -1.5733757395516363, -1.9343054344201707, 6.787212280236046, -0.35603892339489995, -1.3414921239899753, -0.9393551256779856, -1.9298884254368263, 6.043295105337908, 2.9330671137121733, 2.8561036619044047, -0.8293767467550212, 6.123622142714353, -2.2350961485598777, 7.20722805161423, 5.515389689089437, -2.7666432567169745, -4.344590134196103, 3.3453531590362613, 10.413288779778698, 0.3986583788822756, 1.8156402784897105, -6.495232639280744, -2.5586148068696852, 2.456750085945401, -2.0241915465317994, 2.6640207424833706, -3.221638093253812, -0.13291701098446618, 4.525894152095317, 3.833943185257407, -2.892260297173234, -3.247865929061468, 6.129696012756685, 4.451839001858698, -3.142375819178058, -1.0758596832313212, -7.85705595464708, -3.376343621066232, -3.993944532318441, 13.146850947670861, -1.3900676627648902, 3.8600378751921256, 3.9652071948870447, -2.4382860496298324, 3.0864605092488304, -10.769089293963074, 1.9773754511588617, 4.826841112732377, 7.9219782116860324, -3.266132871461332, 1.8118819669439024, 0.698579723806034, 7.119629551067371, -0.9141128559070014, 1.5143207368301361, -8.587596597534729, -0.9387144566983379, 2.5641381148921805, 10.628593146418485, 3.794317923770138, 6.2802756227726615, -0.05171930511667566, 0.8736426098894451, 0.6226851580000003};

    double[] list3 = {9.631212195521316, -2.1235831279282698, 3.7468670477204773, -4.559878135521824, 3.2444286767576545, 6.2877828741148605, 6.520597627024687, 2.642307472836288, 1.2002893113069557, 0.32620641006622675, -3.368962812990781, -2.588868228199504, 4.356518441561512, -0.5955112302723241, 0.3875648501871751, -2.9311051175998064, 2.0095554763173666, -1.228769483871199, 5.900445902470515, 0.41527619439744434, 2.9752128071432145, 4.805920315662717, -4.797853823364673, 5.752192282393844, 2.9073605365834556, 2.4870719041084497, -1.7994046436584152, 7.79554996548367, 4.4174973514255536, 2.084039895979635, 0.6281302992116424, -3.1466915662704524, 3.646400672147826, 0.9609952887592054, -6.070082172976056, -0.9392599054917704, 0.904301836858967, 5.926867039519574, 3.238559698585232, -4.439332575192746, 1.352444182896236, -0.24594080100384297, -1.6395807550351367, 3.591208179788307, 4.15757174804611, -3.5334824535956173, 0.5302366137985215, 9.564674975899017, 4.175389023096817, -0.9827335882191762, 4.305890552392608, 3.059083687714633, 2.3224548745551488, 0.1934380213592375, 1.0235814, 1.1716370685853148, -2.931711339626567, -4.214035402157694, -1.0093422753964358, -4.843082160061708, -7.148710177896536, -1.910725804980465, -0.22905523068711164, 3.8200222938181367, -1.744095856344644, 1.354958988184811, 0.9933832752568843, 0.8820951391051288, -2.062035935350486, -7.633897329029599, 0.49911238393151325, -1.1684033502541722, 4.090099097765502, 4.566828839384462, 0.6901115935421007, -4.30695891725898, -5.637531096381548, 2.6920329212478507, -1.522395621132775, 6.351734133984433, 0.4895678835360122, -4.755548841958967, -2.826990702897114, 1.974618789378563, -6.999938959339396, 0.6289774718852977, 3.2732671487606266, -1.2781272997669557, 6.725303989648547, -7.163688015215646, 5.547683884070125, -3.0189942298996213, -0.2487963910538069, -0.46314538549764894, 5.3913279138183645, -4.018219623545416, 6.491084381355617, -1.5629014732514819, -6.557894883162792, -3.856421007612216};

    double sum2 = 0;

    double evenSum = 0;

    double evenSum2 = 0;

    double sum3 = 0;

    double oddSum = 0;

    double oddSum2 = 0;

    for (int i = 0; i < list2.length; i++) {

        if (list2[i] % .000000000000002 == 0)

            evenSum += list2[i];

        if (list2[i] % .000000000000002 != 0)

            oddSum += list2[i];
    }

    for (int i = 0; i < list3.length; i++) {

        if (list3[i] % .000000000000002 == 0)

            evenSum2 += list3[i];

        if (list3[i] % .000000000000002 != 0)

            oddSum2 += list3[i];
    }

    System.out.println(evenSum);
    System.out.println(oddSum);
    System.out.println(evenSum2);
    System.out.println(oddSum2);

I thought that I would have to match the decimal places with the numbers in the list otherwise I would always get != 0 — eddie, Mar 14 '18 at 23:43

score 2 · Answer 1 · edited Mar 15 '18 at 00:22

2

From Wiki

In mathematics, parity is the property of an integer's inclusion in one of two categories: even or odd. An integer is even if it is evenly divisible by two and odd if it is not even.

The key word here is integer. That means that you can't identify non-integer values as even or odd.

Modulus operator works as it is intened to work - return the remainder of a division operation. Entries of the arrays are not evenly divisible by .000000000000002: that is why you get 0 as a sum of 'even' numbers.

edited Mar 15 '18 at 00:22

user207421

305,947
44
307
483

answered Mar 14 '18 at 23:47

olezhka

41
4

Hi. So would I have to convert them into integers first before trying to use the modulus? – eddie Mar 15 '18 at 01:06
It depends on what you are trying to achieve by dividing these numbers into two categories. Double values cannot be ever or odd by definition. If you really want identify even and odd numbers, change arrays of doubles to arrays of integers. And again, modulus is not an operator for identifying even or odd numbers, it returns the reminder of a division operation. – olezhka Mar 15 '18 at 09:21

Using modulus on a double

1 Answers1