Question

I’m storing a number as a double. It works well with small numbers but if the double is 1000000 and I try to add 10 to it, it doesn’t work but I can add 100 to it. If the double is 100000 and I try to add 1 to it, it doesn’t work but I can add 10 to it.

Is this a problem with using a double? What format should I be using for up to a 9 digit number?

Edit: I’m doing calculations on the number and putting it in a 0.00 decimal format. It works on small numbers but not on big. It might have something to do with the other calculations. Just seeing if maybe double was the problem.

I run into problems when I take 1000001 / 100 and put in 0.00 decimal format. But 1000100 / 100 put into a 0.00 dec format works.

Answer 1

Not sure what you mean by “it doesn’t work”, considering that it should:

System.out.println(1000000d + 10d); // 1000010.0

Cases where it wouldn’t work are where there is a value that is more than about 15 digits from the most significant digit of the largest double involved:

System.out.println(Math.pow(10, 18) + 10d - Math.pow(10, 18)); // 0.0
System.out.println(Math.pow(10, 17) + 10d - Math.pow(10, 17)); // 16.0
System.out.println(Math.pow(10, 16) + 10d - Math.pow(10, 16)); // 10.0