How do I round a float but keep it a float (i.e. without converting it to int)?

Question

for example i have a result of circle area = 4.3, my question is 'when i get number grater than .5 [for example(4.6, 4.7, 4.8, 4.9)], i want it to give me 5.0, but if less than .5 [4.4, 4.3, 4.2, 4.1] then show me 4.0'

i tried Math.round() but it converts float to int like [4], but i don't want to convert it to int

is there a way to do this?

here is my code:

private float radius;
private double result;

public void show(float x)
{
    this.radius = x;
    this.result=Math.pow(x,2)*Math.PI;

    System.out.println("result is: "+result);
}

clearly, i want both method(Math.floor()) and (Math.ceil()) in one function thanks

`Math.round(4.5f)` will return 5 and do exactly what you want. And converting an int to a float/double really isn't that hard at all. — OH GOD SPIDERS, Jan 15 '18 at 12:31
Alternatively, since you know the area will always be positive, you could use `Math.floor( area + .5 )`. — Thomas, Jan 15 '18 at 12:33
`(float)Math.round(x)` makes the int again a float. However `float` and `double` are an approximation (of sums of powers of 2), without fixed number of decimals, and 5.3 has in reality a small error, 10000*5.3 will not be exactly 53000. — Joop Eggen, Jan 15 '18 at 12:34
[Rounding a double to turn it into an int (java)](https://stackoverflow.com/q/2654839) — Bernhard Barker, Jan 15 '18 at 12:41
@Thomas wow, this is exactly what i want! thank you very much — mhamad arsalan, Jan 15 '18 at 12:44
@Dukeling yes it works, but i don't want to convert float to int, i want to keep the float point, like(if the point >.5, floor it, and if the point <.5, ceil it) thanks — mhamad arsalan, Jan 15 '18 at 12:49
@JoopEggen thanks, it works =), but for ("10000*5.3") , I tried windows calculator and it gives me exactly 53000! i don't know if windows has it's own exception handler — mhamad arsalan, Jan 15 '18 at 12:56
The Windows calculator internally does not use float/double, but something like what is BigDecimal in java. — Joop Eggen, Jan 15 '18 at 13:03
@JoopEggen it's strange to me, i mean i'm beginner of codding in java i absolutely have no idea about what you mean by ("windows calculator internally does not use float/double")(sorry for that) or maybe because my English is bad(i don't understand too much English) . sorry, thanks :) — mhamad arsalan, Jan 15 '18 at 13:16
To avoid be able to calculate more precise, with a precision after the decimal point, java has the class BigDecimal. There `12.01 * 4.0` is exactly `48.040`. (BTW only about 10% of the world are good English speakers, and the number is slowly diminishing.) — Joop Eggen, Jan 15 '18 at 14:04

score 0 · Answer 1 · answered Jan 16 '18 at 17:23

0

Math.rint is probably closest to what you're looking for. Note that it rounds half to even.

answered Jan 16 '18 at 17:23

Simon Byrne

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How do I round a float but keep it a float (i.e. without converting it to int)?

1 Answers1