I have below piece of code:
I am passing value "55.00000000000000" and getting output as 55.00000000000001.
But when i passed "45.00000000000000" and "65.00000000000000" i get output as 45.0 and 65.0.
Can someone please help me to get correct output as 55.0.
NumberFormat numberFormat = NumberFormat.getPercentInstance(Locale.US);
if (numberFormat instanceof DecimalFormat) {
DecimalFormat df = (DecimalFormat) numberFormat;
df.setNegativePrefix("(");
df.setNegativeSuffix("%)");
}
Number numericValue = numberFormat.parse("55.00000000000000%");
numericValue = new Double(numericValue.doubleValue() * 100);
System.out.println(numericValue);
The problem here is that numericValue is mathematically supposed to be 0.55. However, it will be a Double (because numberFormat.parse() can only return a Long or a Double). And a Double cannot hold the value 0.55 exactly. See this link for a complete explanation of why. The result is that as you do further computations with the inexact value, roundoff errors will occur, which is why the result being printed out is not quite the exact value. (A Double also cannot be exactly 0.45 or 0.65; it just happens that when multiplying by 100, the result rounds to the correct integer.)
When dealing with decimal values such as money or percentages, it's preferable to use BigDecimal. If the NumberFormat is a DecimalFormat, you can set things up so that parse returns a BigDecimal:
if (numberFormat instanceof DecimalFormat) {
DecimalFormat df = (DecimalFormat) numberFormat;
df.setNegativePrefix("(");
df.setNegativeSuffix("%)");
df.setParseBigDecimal(true); // ADD THIS LINE
}
Now, when you use numberFormat.parse(), the Number it returns will be a BigDecimal, which is able to hold the exact value 0.55. Now you have to avoid converting it to a double, which will introduce a roundoff error. Instead, you should say something like
Number numericValue = numberFormat.parse("55.00000000000000%");
if (numericValue instanceof BigDecimal) {
BigDecimal bdNumber = (BigDecimal) numericValue;
// use BigDecimal operations to multiply by 100, then print or format
// or whatever you want to do
} else {
// you're stuck doing things the old way, you might get some
// inaccuracy
numericValue = new Double(numericValue.doubleValue() * 100);
System.out.println(numericValue);
}
use this line of code
System.out.println(String.format("%.1f", numericValue));
Where format method use to format your data.
Related
I need to return BigDecimal in this format (%.##)
For example i have this floating number
3.2->3.20
6.2->6.20
112.0->112.00
I'm trying this
BigDecimal precoDecial = new BigDecimal(preco);
precoDecial.setScale(2, BigDecimal.ROUND_HALF_UP);
But it is not working for me; this returns:
for:
3.2->3.2000000476837158203125
6.2->6.2
My log with the code reference
BigDecimal precoDecial = new BigDecimal(1.0);
precoDecial = precoDecial.setScale(2, BigDecimal.ROUND_HALF_UP);
System.out.println(precoDecial);
I tried this in my IDE it worked better give it a try hope my work may solve your problem
output
if 1-->1.00
if 1.0-->1.00
if 1.00000000-->1.00
Here is my simple code
#Override
public void onClick(View v) {
try {
double price = Double.parseDouble(ePrice.getText().toString());
double percent = Double.parseDouble(ePercent.getText().toString());
double priceValue = price * percent/100.0f;
double percentValue = price - priceValue;
moneyToGet.setText(String.valueOf(priceValue));
moneyToPay.setText(String.valueOf(percentValue));
moneyToGet.setText("" + priceValue);
moneyToPay.setText("" + percentValue);
// catch
} catch (NumberFormatException ex) {
// write a message to users
moneyToGet.setText("");
}
}
});
This is a simple code for Percentage Calculator.
What I want is to avoid the Scientific Notation in my Calculator cause I don't want to explain to user what is Scientific Notation.
For example if I want to calculate 100,000,000 and cut 50% of it, it Should give me 50,000,000 which is giving me 5.0E7 And in my case this doesn't make any sense to the user. And of course I know both results are correct.
Thanks in Advance.
Check answer here. You can write
moneyToGet.setText(String.format("%.0f", priceValue));
You can try this DecimalFormat
DecimalFormat decimalFormatter = new DecimalFormat("############");
number.setText(decimalFormatter.format(Double.parseDouble(result)));
I would suggest using BigDecimals instead of doubles. That way you will have a more precise control over your calculation precision. Also you can get a non-scientific String using BigDecimal.toPlainString().
DecimalFormat decimalFormatter = new DecimalFormat("##.############");
decimalFormatter.setMinimumFractionDigits(2);
decimalFormatter.setMaximumFractionDigits(15);
This option will help you ##.## suffix 0 before decimal, otherwise output will be .000
btc.setText(decimalFormatter.format(btcval));
use this for displaying content
Use NumberFormater like
NumberFormat myformatter = new DecimalFormat("########");
String result = myformatter.format(yourValue);
I have been trying to write a java code to Round a value to the below requirement.
If x=63.88 => roundedValue= 64.00;
If x=63.50 => roundedValue= 64.00
If x=63.32 => roundedValue= 63.32
I tried with the different roundingModes like CEILING, DOWN, FLOOR, HALFDOWN.
I also tried Math.round();
But I'm unable to get the expected output.
My input is a string and output is a string.
Please find the code snippet I tried below
BigDecimal value1 = new BigDecimal(input);
value1=value1.setScale(2, RoundingMode.HALF_EVEN);
//float rounded=Math.round(amount);
String finalValue=String.valueOf(value1);
I'm unable to get the desired output. Please let me know how to achieve this?
ps: should i consider using float or BigDecimal??
if(x%1 >= .5)
{ x = Math.round(x) }
else //do nothing
This seems like it would give you the desired output you are looking for. So if you really wanted to you could override or create your own method to call for the rounding
What you want to do with this, is providing your own MathContext to specify the behavior of the rounding you want to perform.
The closest you will get to your current requirements is either: using RoundingMode.HALF_UP or RoundingMode.UNNECESSARY
For that you will have to use BigDecimal anyways, since Double and Float do not expose rounding.
public static void main(String args[]) {
Double d = 63.18;
DecimalFormat df = new DecimalFormat("00.00");
if(d % 1 >= 0.5)
System.out.println(df.format(Math.round(d)));
else
System.out.println(d);
}
As in your post, using BigDecimal is the way to go, if you want to use decimal rounding.
If you want to round up for numbers >= X.5 and avoid rounding for numbers < X.5 then you can use this code:
import java.math.BigDecimal;
import java.math.RoundingMode;
public class Round {
public static void main(String[] args) {
System.out.println(round("63.88"));
System.out.println(round("63.50"));
System.out.println(round("63.32"));
}
private static BigDecimal round(String input) {
BigDecimal value = new BigDecimal(input);
BigDecimal rounded = value.setScale(0, RoundingMode.HALF_UP);
if (rounded.compareTo(value) > 0)
return rounded.setScale(2);
return value;
}
}
The output is:
64.00
64.00
63.32
In a web application ,I want to model an ItemForSale which has a price field.I read elsewhere that float or double should not be used for currency fields due to rounding errors and BigDecimal is the proper type for this purpose.I created these classes
class ItemForSale {
private String name;
private BigDecimal price;
...
}
class MyUtils{
...
public static BigDecimal parsePriceOfItem(String priceStr){
BigDecimal price;
BigDecimal zero = new BigDecimal(0);
try{
price = new BigDecimal(priceStr);
}catch(NumberFormatException nfe){
price = zero;
}
if(price.doubleValue() < zero.doubleValue()){
price = zero;
}
return price;
}
}
Is this the right way to parse a price string(as entered by user)?I wanted to treat negative and invalid strings (say 'abcd') as 0.
If there is a better way ,please tell me
thanks
mark
Why would you want to treat invalid input as 0? Surely you'd want to tell the user that they've made a mistake, rather than treating it as if they'd typed in zero.
If you're parsing user input, you should probably be using DecimalFormat instead of the BigDecimal constructor - that way it will use the appropriate cultural information. (Use setParseBigDecimal to make DecimalFormat parse to BigDecimal instead of double.)
Then instead of converting the BigDecimal values to doubles, use:
if (price.compareTo(BigDecimal.ZERO) < 0)
I would suggest that you should indicate to the user three different states:
Number can't be parsed
Number was negative (or possibly invalid in some other way; do you have a maximum value, or a maximum number of digits)?
Number was valid
How costly is your most expensive item? If it is less than $21,474,836.47 you can safely express the price as a number of cents held in a normal int.
You are correct to avoid float and double. The usual solution is to use an int, or a long, to hold the number of cents and adjust output formatting accordingly. There is usually no need to get into the complexities, and speed issues, of BigDecimal.
Here's my suggestion:
public static BigDecimal parsePriceOfItem(String priceStr) {
try {
BigDecimal price = new BigDecimal(priceStr);
return price.compareTo(BigDecimal.ZERO) < 0 ? BigDecimal.ZERO : price;
} catch(NumberFormatException nfe) {
return BigDecimal.ZERO;
}
}
I was trying to make my own class for currencies using longs, but apparently I should use BigDecimal instead. Could someone help me get started? What would be the best way to use BigDecimals for dollar currencies, like making it at least but no more than 2 decimal places for the cents, etc. The API for BigDecimal is huge, and I don't know which methods to use. Also, BigDecimal has better precision, but isn't that all lost if it passes through a double? if I do new BigDecimal(24.99), how will it be different than using a double? Or should I use the constructor that uses a String instead?
Here are a few hints:
Use BigDecimal for computations if you need the precision that it offers (Money values often need this).
Use the NumberFormat class for display. This class will take care of localization issues for amounts in different currencies. However, it will take in only primitives; therefore, if you can accept the small change in accuracy due to transformation to a double, you could use this class.
When using the NumberFormat class, use the scale() method on the BigDecimal instance to set the precision and the rounding method.
PS: In case you were wondering, BigDecimal is always better than double, when you have to represent money values in Java.
PPS:
Creating BigDecimal instances
This is fairly simple since BigDecimal provides constructors to take in primitive values, and String objects. You could use those, preferably the one taking the String object. For example,
BigDecimal modelVal = new BigDecimal("24.455");
BigDecimal displayVal = modelVal.setScale(2, RoundingMode.HALF_EVEN);
Displaying BigDecimal instances
You could use the setMinimumFractionDigits and setMaximumFractionDigits method calls to restrict the amount of data being displayed.
NumberFormat usdCostFormat = NumberFormat.getCurrencyInstance(Locale.US);
usdCostFormat.setMinimumFractionDigits( 1 );
usdCostFormat.setMaximumFractionDigits( 2 );
System.out.println( usdCostFormat.format(displayVal.doubleValue()) );
I would recommend a little research on Money Pattern. Martin Fowler in his book Analysis pattern has covered this in more detail.
public class Money {
private static final Currency USD = Currency.getInstance("USD");
private static final RoundingMode DEFAULT_ROUNDING = RoundingMode.HALF_EVEN;
private final BigDecimal amount;
private final Currency currency;
public static Money dollars(BigDecimal amount) {
return new Money(amount, USD);
}
Money(BigDecimal amount, Currency currency) {
this(amount, currency, DEFAULT_ROUNDING);
}
Money(BigDecimal amount, Currency currency, RoundingMode rounding) {
this.currency = currency;
this.amount = amount.setScale(currency.getDefaultFractionDigits(), rounding);
}
public BigDecimal getAmount() {
return amount;
}
public Currency getCurrency() {
return currency;
}
#Override
public String toString() {
return getCurrency().getSymbol() + " " + getAmount();
}
public String toString(Locale locale) {
return getCurrency().getSymbol(locale) + " " + getAmount();
}
}
Coming to the usage:
You would represent all monies using Money object as opposed to BigDecimal. Representing money as big decimal will mean that you will have the to format the money every where you display it. Just imagine if the display standard changes. You will have to make the edits all over the place. Instead using the Money pattern you centralize the formatting of money to a single location.
Money price = Money.dollars(38.28);
System.out.println(price);
Or, wait for JSR-354. Java Money and Currency API coming soon!
1) If you are limited to the double precision, one reason to use BigDecimals is to realize operations with the BigDecimals created from the doubles.
2) The BigDecimal consists of an arbitrary precision integer unscaled value and a non-negative 32-bit integer scale, while the double wraps a value of the primitive type double in an object. An object of type Double contains a single field whose type is double
3) It should make no difference
You should have no difficulties with the $ and precision. One way to do it is using System.out.printf
Use BigDecimal.setScale(2, BigDecimal.ROUND_HALF_UP) when you want to round up to the 2 decimal points for cents. Be aware of rounding off error when you do calculations though. You need to be consistent when you will be doing the rounding of money value. Either do the rounding right at the end just once after all calculations are done, or apply rounding to each value before doing any calculations. Which one to use would depend on your business requirement, but generally, I think doing rounding right at the end seems to make a better sense to me.
Use a String when you construct BigDecimal for money value. If you use double, it will have a trailing floating point values at the end. This is due to computer architecture regarding how double/float values are represented in binary format.
Primitive numeric types are useful for storing single values in memory. But when dealing with calculation using double and float types, there is a problems with the rounding.It happens because memory representation doesn't map exactly to the value. For example, a double value is supposed to take 64 bits but Java doesn't use all 64 bits.It only stores what it thinks the important parts of the number. So you can arrive to the wrong values when you adding values together of the float or double type.
Please see a short clip https://youtu.be/EXxUSz9x7BM
I would be radical. No BigDecimal.
Here is a great article
https://lemnik.wordpress.com/2011/03/25/bigdecimal-and-your-money/
Ideas from here.
import java.math.BigDecimal;
public class Main {
public static void main(String[] args) {
testConstructors();
testEqualsAndCompare();
testArithmetic();
}
private static void testEqualsAndCompare() {
final BigDecimal zero = new BigDecimal("0.0");
final BigDecimal zerozero = new BigDecimal("0.00");
boolean zerosAreEqual = zero.equals(zerozero);
boolean zerosAreEqual2 = zerozero.equals(zero);
System.out.println("zerosAreEqual: " + zerosAreEqual + " " + zerosAreEqual2);
int zerosCompare = zero.compareTo(zerozero);
int zerosCompare2 = zerozero.compareTo(zero);
System.out.println("zerosCompare: " + zerosCompare + " " + zerosCompare2);
}
private static void testArithmetic() {
try {
BigDecimal value = new BigDecimal(1);
value = value.divide(new BigDecimal(3));
System.out.println(value);
} catch (ArithmeticException e) {
System.out.println("Failed to devide. " + e.getMessage());
}
}
private static void testConstructors() {
double doubleValue = 35.7;
BigDecimal fromDouble = new BigDecimal(doubleValue);
BigDecimal fromString = new BigDecimal("35.7");
boolean decimalsEqual = fromDouble.equals(fromString);
boolean decimalsEqual2 = fromString.equals(fromDouble);
System.out.println("From double: " + fromDouble);
System.out.println("decimalsEqual: " + decimalsEqual + " " + decimalsEqual2);
}
}
It prints
From double: 35.7000000000000028421709430404007434844970703125
decimalsEqual: false false
zerosAreEqual: false false
zerosCompare: 0 0
Failed to devide. Non-terminating decimal expansion; no exact representable decimal result.
How about storing BigDecimal into a database? Hell, it also stores as a double value??? At least, if I use mongoDb without any advanced configuration it will store BigDecimal.TEN as 1E1.
Possible solutions?
I came with one - use String to store BigDecimal in Java as a String into the database. You have validation, for example #NotNull, #Min(10), etc... Then you can use a trigger on update or save to check if current string is a number you need. There are no triggers for mongo though.
Is there a built-in way for Mongodb trigger function calls?
There is one drawback I am having fun around - BigDecimal as String in Swagger defenition
I need to generate swagger, so our front-end team understands that I pass them a number presented as a String. DateTime for example presented as a String.
There is another cool solution I read in the article above...
Use long to store precise numbers.
A standard long value can store the current value of the Unites States national debt (as cents, not dollars) 6477 times without any overflow. Whats more: it’s an integer type, not a floating point. This makes it easier and accurate to work with, and a guaranteed behavior.
Update
https://stackoverflow.com/a/27978223/4587961
Maybe in the future MongoDb will add support for BigDecimal.
https://jira.mongodb.org/browse/SERVER-1393
3.3.8 seems to have this done.
It is an example of the second approach. Use scaling.
http://www.technology-ebay.de/the-teams/mobile-de/blog/mapping-bigdecimals-with-morphia-for-mongodb.html
There is an extensive example of how to do this on javapractices.com. See in particular the Money class, which is meant to make monetary calculations simpler than using BigDecimal directly.
The design of this Money class is intended to make expressions more natural. For example:
if ( amount.lt(hundred) ) {
cost = amount.times(price);
}
The WEB4J tool has a similar class, called Decimal, which is a bit more polished than the Money class.
NumberFormat.getNumberInstance(java.util.Locale.US).format(num);