I am trying to round float number but with certain condition. If second decimal point larger or equal 9 round up end else round down. Can you please help me this?
//0.56 -> 0.5
//1.56 -> 1.5
//1.58 -> 1.5
//1.59 -> 1.6
//15.56 -> 15.5
To round up at 0.09, and round down at 0.089999999..., you add 0.01 and truncate to 1 fractional digit.
Truncating positive floating point values can be done using the Math.floor() method, like this:
Math.floor(value * 10 + 0.1) / 10
UPDATE
Since a number like 0.59 is actually 0.58999999999999996, it gets rounded down, when the intent is to round up.
One way to get around "broken floating point math", is to use BigDecimal:
BigDecimal.valueOf(value).add(new BigDecimal("0.01")).setScale(1, RoundingMode.DOWN)
If you do this a lot, the new BigDecimal("0.01") value should be created as a static final constant.
Note: As with the first solution, this only works for positive numbers.
This works good.
float n = 1.7912f;
n = n*100.0f;
long a = (int) n;
if (a % 10 >=9) {
a=a+1;
}
n = (float) a / 100.0f;
System.out.println(n);
One of the different solution would be to check the last digit.
float number = number*100;
if (number % 10 >=9) {
number = number + (10-(number % 10));
} else {
number = number - (number % 10);
}
number = number / 100;
Here's my homemade solution. Make a substring of the float's string value which starts two characters after the decimal and ends three characters after the decimal (would look like this: inputString=".56" subString="6"). Get the integer value of that substring and compare it to 9. If it is greater than or equal to, add another tenth. Otherwise trim the float from the hundredths place and move on. It's not very pretty, but it works:
public static void main(String[] args) {
long current = System.currentTimeMillis();
System.out.println(doWierdOperation(0.56F) + " - " + (System.currentTimeMillis()-current) + "ms.");
current = System.currentTimeMillis();
System.out.println(doWierdOperation(1.56F) + " - " + (System.currentTimeMillis()-current) + "ms.");
current = System.currentTimeMillis();
System.out.println(doWierdOperation(1.58F) + " - " + (System.currentTimeMillis()-current) + "ms.");
current = System.currentTimeMillis();
System.out.println(doWierdOperation(1.59F) + " - " + (System.currentTimeMillis()-current) + "ms.");
current = System.currentTimeMillis();
System.out.println(doWierdOperation(15.56F) + " - " + (System.currentTimeMillis()-current) + "ms.");
}
public static float doWierdOperation(float val) {
String sValue = String.valueOf(val);
int dec = sValue.indexOf(".");
if (sValue.charAt(dec + 2) == '9') {
// Increment at tenths palce
val += 0.1F;
}
// Trim from hundredth place
return Float.valueOf(String.valueOf(val).substring(0, dec + 2));
}
First run:
0.5 - 3ms.
1.5 - 0ms.
1.5 - 0ms.
1.6 - 0ms.
15.5 - 0ms.
Second run:
0.5 - 3ms.
1.5 - 0ms.
1.5 - 0ms.
1.6 - 0ms.
15.5 - 0ms.
Third run:
0.5 - 2ms.
1.5 - 0ms.
1.5 - 0ms.
1.6 - 0ms.
15.5 - 0ms.
