Viewed 1. I know one method of doing this is to use the String. What I'd like is this: 0. Alex Spurling Alex Spurling Add a comment. Active Oldest Votes. This is probably the best solution presented so far. The reason I didn't spot this facility when I first looked at the DecimalFormat class is that it was only introduced in Java 1.
Unfortunately I'm restricted to using 1. I tried this with: ". Please be carefull as DecimalFormat depend on your current Local configuration, you may not get a dot as a separator. I personnally prefer Asterite's answer below — Gomino. Also be aware that you should not expect DecimalFormat to be thread-safe. As per Java docs : Decimal formats are generally not synchronized. It is recommended to create separate format instances for each thread. If multiple threads access a format concurrently, it must be synchronized externally.
Show 5 more comments. Assuming value is a double , you can do: double Math. The number of zeros indicate the number of decimals. I looped using DecimalFormat times, and this method. DecimalFormat took 14ms to complete the loops, this method took less than 1ms.
As I suspected, this is faster. If you get paid by the clock cycle, this is what you should be doing. I'm surprised Chris Cudmore would even say what he said to be honest. Indeed, this fails: Math. Be very careful when using this method or any rounding of floating points.
It fails for something as simple as The intermediate result of This means it gets rounded down to There simply are inherent problems when converting from floating point numbers to real decimal numbers. See EJP's answer here at stackoverflow. SebastiaanvandenBroek: Wow I never knew it was that easy to get a wrong answer.
However, if one is working with non-exact numbers, one must recognize that any value is not exact. We do not know the true, exact value. At the edge values, either answer is arguably correct. If we need to be exact, we shouldn't work in double. The fail here isn't in converting back to double. Its in OP thinking he can rely on the incoming Show 15 more comments. Sample program: package trials; import java.
Nav MetroidFan MetroidFan 28k 16 16 gold badges 61 61 silver badges 79 79 bronze badges. That's my preferred solution. Even shorter: BigDecimal. Don't cut corners and use new BigDecimal doubleVar as you can run into issues with rounding of floating points — Edd. Edd, interestingly, the rounding issue occurs in the case SebastiaanvandenBroek mentions in comment to asterite's answer.
ToolmakerSteve That's because using new BigDecimal with the double takes the double value directly and attempts to use that to create the BigDecimal, whereas when using BigDecimal. There's a big trade off between accuracy and speed, as the method specified by asterite is much faster, but rounds to errors. So if you're just removing decimals in order to store a GPS bearing with only one decimal into a JSON string, you probably don't need all the precision of this expensive method.
Milhous Milhous I believe one of the goals of the question was that "there should not be any trailing zeroes". For this question, the op didn't want zeros, but this is exactly what I wanted. If you have a list of numbers with 3 decimal places, you want them to all have the same digits even if it's 0. You forgot to specify RoundingMode. IgorGanapolsky by default Decimal mode uses RoundingMode. ONE, mc. The trick is that in all of your errors, the printed result is still correct. DidierL It doesn't surprise me.
I had the very good fortune of doing 'Numerical Methods' as my very first computing course and being introduced right at the start to what floating-point can and cannot do. Most programmers are pretty vague about it. Python Turtle. Verbal Ability.
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Data Structures. Operating System. As we saw in the previous section dividing two integers and getting the result in a integer variable, leads to a Round to zero behaviour. While we understand the division of two integer number in java, we get a round to zero behavior. This does not mean we lost out the decimal portion. Java comes with two methods Math. The code show usage of this two methods. At times, we want specific behavior for rounding up or rounding down.
Ceil and Floor are functions in Java which give you nearest integer down or up. The java math library provides a static ceil function which accepts a double. The ceil method returns the smallest double value that is greater than or equal to equal to the argument and is equal to a mathematical integer. The java math library provides a static floor function which accepts a double. The floor method returns the largest double value that is less than or equal to the argument and is equal to a mathematical integer.
Parameters: rm - legacy integer rounding mode to convert Returns: RoundingMode corresponding to the given integer. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy. Object java. Each rounding mode indicates how the least significant returned digit of a rounded result is to be calculated.
If fewer digits are returned than the digits needed to represent the exact numerical result, the discarded digits will be referred to as the discarded fraction regardless the digits' contribution to the value of the number. In other words, considered as a numerical value, the discarded fraction could have an absolute value greater than one. Rounding mode to round towards "nearest neighbor" unless both neighbors are equidistant, in which case round down. Rounding mode to round towards the "nearest neighbor" unless both neighbors are equidistant, in which case, round towards the even neighbor.
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