Android Divide number with decimal fraction

Question

How can i check number is divisible by particular number or not both numbers are decimal. with decimal point value of two digits. i had tried with below (((dn / size) % 1) == 0) but in some cases it not provide proper out put. how can i resolve it. here i put some example values like double dn = 369.35,369.55.370.55 and size may be 0.05,0.10,0.5 etc...

 if(((dn / size) % 1) == 0)    {
       Log.d(TAG,"OK");
    } else {
       Log.d(TAG,"OK");
    }

please help me to short out it.

above values are proper and they are not static they may change. and output is that i want to check weather is number is divisible by size or not if not then show toast else not. — Madhav_nimavat, Jul 17 '17 at 10:50
Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/149371/discussion-between-droidev-and-madhav-nimavat). — droidev, Jul 17 '17 at 10:52

Bathsheba · Answer 1 · 2017-07-17T11:09:35.513

1

(dn / size) % 1 == 0 whilst plausible, will suffer from pitfalls centred around binary floating point arithmetic.

If your numbers always have no more then two decimal places then the easiest thing to do is scale up by multiplying by 100 and rely on the fact that 100 * y divides 100 * x if y divides x. In other words:

if (Math.round(100 * dn) % Math.round(100 * size) == 0){
    Log.d(TAG,"Divisible");
} else {
    Log.d(TAG,"Not divisible");
}

This obviates any issues with binary floating point arithmetic. I've used Math.round rather than a truncation deliberately, again to obviate issues around floating point and am relying on what is in my opinion a quirk of this platform in that round returns an integral type.

Further reading: Is floating point math broken?

edited Jul 17 '17 at 11:09

answered Jul 17 '17 at 10:44

Bathsheba

231,907
34
361
483

I cannot round size value – Madhav_nimavat Jul 17 '17 at 11:06
if i round 0.05 it return 5 which is not ok – Madhav_nimavat Jul 17 '17 at 11:07
What do you mean? – Bathsheba Jul 17 '17 at 11:07
That doesn't matter since you're also multiplying up `dn`. Try it! – Bathsheba Jul 17 '17 at 11:07
E.g. exact divisibility of 37042 by 5 is the same as 370.42 by 0.05. Mathematically, that is. – Bathsheba Jul 17 '17 at 11:08

droidev · Answer 2 · 2017-07-17T14:11:15.507

0

You are doing it wrongly,

try with this code

if(dn % size  == 0)    {
  Log.d(TAG,"Divisible");
} else {
   Log.d(TAG,"Not divisible");
}

Update

Use BigDecimal in case you have big decimal numbers

eg :

BigDecimal bg1, bg2, bg3;

bg1 = new BigDecimal("513.54");
bg2 = new BigDecimal("5");

// bg2 divided by bg1 gives bg3 as remainder
bg3 = bg1.remainder(bg2);

edited Jul 17 '17 at 14:11

answered Jul 17 '17 at 10:52

droidev

7,352
11
62
94

No it won't in general due to floating point joke digits. You'll get lucky with dyadic rationals. – Bathsheba Jul 17 '17 at 10:57
370.42 %0.05 return 0.019999999999995355 and 370.45%0.05 returns 0.049999999999956704 – Madhav_nimavat Jul 17 '17 at 11:00
in that case either you have to use double or BigDecimal – droidev Jul 17 '17 at 11:01
how can i used it please give me demo – Madhav_nimavat Jul 17 '17 at 11:04

Android Divide number with decimal fraction

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