Java DecimalFormat problem - java

I would like to format numbers of type double with a German locale in Java. However something goes wrong since the output of the following code is : 0.0
package main;
import java.text.DecimalFormat;
import java.text.NumberFormat;
import java.text.ParseException;
import java.util.Locale;
public class Test {
private static String decimal2Format = "000.000";
public static void main(String args[]){
DecimalFormat format = (DecimalFormat)NumberFormat.getInstance(new Locale("de"));
double value = 0;
try {
format.applyPattern(decimal2Format);
value = format.parse("0.459").doubleValue();
} catch (ParseException e) {
e.printStackTrace();
}
System.out.println(value);
}
}
Do you have any ideas what is wrong or missing?
Thanks,
atticus

You're trying to parse using a pattern which will expect a comma (as it's in German) but you've given it a period ("0.459"). It looks like DecimalFormat stops parsing when it sees a character it doesn't understand. If you change it to "0,459" you'll see it parse correctly and then output "0.459". (I'm not sure whether System.out.println uses the system default locale, in which case it might print "0,459" depending on your locale.)
Note that you haven't tried to format the number at all in this code - only parse a number. If you want to format it, call format. The double itself doesn't have an associated format - it's just a number. It's not like parsing using a particular formatter returns a value which retains that format.
Here's code which will perform actual formatting of a double value:
DecimalFormat format = (DecimalFormat)NumberFormat.getInstance(new Locale("de"));
double value = 0.459;
String formatted = format.format(value);
System.out.println(formatted); // Prints "0,459"
EDIT: Okay, so it sounds like you're converting it from one format to another (from US to European, for example). That means you should probably use two different DecimalFormat objects - you could switch the locale between calls, but that sounds a bit grim to me.
I believe one way to parse and detect errors is to use the parse overload which takes a ParsePosition as well. Set the position to 0 to start with, and afterwards check that it's at the end of the string - if it isn't, that means parsing has effectively failed. I find it odd that there isn't a method which does this automatically and throws an exception, but I can't see one...
You may also want to set the parser to produce a BigDecimal instead of a double, if you're dealing with values which are more logically decimal in nature. You can do this with the setParseBigDecimal method.

Related

dont quite understand string.format, and the java documentation

i couldnt find anything specific for this, so i was wondering how do i use string format to make a double value output in exactly this format $XXXX.XX, could anyone show me how this is done, and break each piece of the method down of what it is actually doing because i just dont know how to apply what i see on the docs im using to what im trying to output in the method and i would much rather understand what each 'command/argument' means or does so that I dont have to ask a question like this.
https://www.javatpoint.com/java-string-format // the docs im using
the code im trying to format,
value taken from explicit
double dollarAmt = String.format(????);
so i was wondering how do i use string format to make a double value
output in exactly this format $XXXX.XX
There are a lot of ways to do that. Here is one:
import java.text.DecimalFormat;
import java.text.NumberFormat;
...
double someNumber = 21.12;
NumberFormat formatter = new DecimalFormat("$0000.00");
String result = formatter.format(someNumber);

NumberFormat doesn't crash with 2 decimal separators

I have a question regarding the behavior of the NumberFormat:
When I want to translate/parse a formatted String into a Number, then I would like to use NumberFormat, since it provides me with nice presets for thousand and decimal separators. Additionally I would like it to crash, if the provided String is not a valid Number.
An example:
// works as expected
String testInput1 = "3,1415";
NumberFormat germanNumberFormat = NumberFormat.getInstance(Locale.GERMANY);
Number number1 = germanNumberFormat.parse(testInput1);
System.out.println(number1); // prints 3.1415
// does not work as expected, cuts off the number after the 2nd decimal
// separator, expected it to crash with java.lang.NumberFormatException:
// multiple points
String testInput2 = "3,14,15";
Number number2 = germanNumberFormat.parse(testInput2);
System.out.println(number2); // prints 3.14
I currently use Double.parseDouble(String s), to have this additional behavior:
// crashes with java.lang.NumberFormatException: multiple points
double number2WithError = Double.parseDouble(testInput2.replace(",", "."));
Is there a way I can use NumberFormat to have my required/expected behavior besides writing my own wrapper class that does some additional checks on e.g. multiple decimal separators?
Also I'm aware that the JavaDoc of the used parse(String source) method of NumberFormat says:
Parses text from the beginning of the given string to produce a number. The method may not use the entire text of the given string.
See the {#link #parse(String, ParsePosition)} method for more information on number parsing.
and parse(String source, ParsePosition parsePosition):
Returns a Long if possible (e.g., within the range [Long.MIN_VALUE, Long.MAX_VALUE] and with no decimals), otherwise a Double. If IntegerOnly is set, will stop at a decimal point (or equivalent; e.g., for rational numbers "1 2/3", will stop after the 1). Does not throw an exception; if no object can be parsed, index is unchanged!
This doesn't tell me though why the method behaves this way. What I get from these is that they can parse only parts of the String (what they obviously do here) and probably just start parsing at the beginning (start position) until they find something they can't deal with.
I didn't find an existing question covering this, so if there is already one, please feel free to close this post and please link to it.
NumberFormat.parse(String) is behaving exactly as documented:
Parses text from the beginning of the given string to produce a number. The method may not use the entire text of the given string.
(Emphasis added)
You ask:
Is there a way I can use NumberFormat to have my required/expected behavior besides writing my own wrapper class that does some additional checks on e.g. multiple decimal separators?
You cannot provide a format that will make NumberFormat.parse() throw an exception for input with only an initial substring that can be parsed according to the format. You can, however, use NumberFormat.parse(String, ParsePosition) to determine whether the whole input was parsed, because the parse position argument is used not only to indicate to the method where to start, but also for the method to say where it stopped. That would be a lot better than implementing format-specific extra checks. Example:
ParsePosition position = new ParsePosition(0);
Number result = format.parse(input, position);
if (position.getIndex() != input.length()) {
throw new MyException();
}
Additionally, you write:
This doesn't tell me though why the method behaves this way.
It behaves that way because sometimes parsing the initial portion of the input is exactly what you want to do. You can build stricter parsing on top of more relaxed parsing, as shown, but it's much more difficult to do it the other way around.

NumberFormat.format() returns inconsistent values

I am parsing multiple files in parallel, and from times to times, the format() method will not return the right value.
Number parse = numberFormat.parse(val);
String format = numberFormat.format(parse);
format.equals(parse); //returns false sometimes
At first I thought it was due to the fact that the format method was not thread safe, but it was using a numberformat.clone() for each thread.
I also tried creating a new NumberFormat() for each thread, and also a ThreadLocal<NumberFormat>, with an initial value, and then calling the get() method, all with the same problem.
In the debugger, an evaluation of the expression always return the right value at the breakpoint.
I tried putting multiple lines String format = numberFormat.format(parse);, it turns out that randomly, one or several of the lines return a completely wrong value, and the other return the right one.
I'm 99% sure it's a thread issue, and a concurrent access is made to something, probably the numberFormat itself.
I might not have used the right way to make it thread safe, but in my understanding, using either clone() or new should get rid of that concern.
Any clues as to what is causing the issue, and how to fix it?
EDIT :
Here are two screen shots made with IntelliJ IDEA to showcase the issue :
Extend the NumberFormat class and synchronize the format method:
class SynchronizedNumberFormat extends NumberFormat {
public synchronized String format(Number number) {
return super.format(number);
}
//unimplemented methods...
}
There has never been any guarantee that a NumberFormat's format method will return exactly the same String as what you parsed the number from. In fact, many Strings can yield the same Number value.
First, consider trailing zeroes:
NumberFormat numberFormat = NumberFormat.getInstance();
Number parsed = numberFormat.parse("1.500000000000");
String formatted = numberFormat.format(parsed);
System.out.println(formatted); // prints 1.5
Second, NumberFormat doesn't parse a complete String like the Double.valueOf, Integer.valueOf, etc. It parses as much as it can from the String, and ignores trailing characters. The following are all valid operations that will parse successfully, without throwing a ParseException:
NumberFormat numberFormat = NumberFormat.getInstance();
numberFormat.parse("1.500000000000");
numberFormat.parse("1.5 ");
numberFormat.parse("1.5-----------");
numberFormat.parse("1.5helloworld");
All of the above calls return 1.5.

How to divide the value of a field in a tmap in TALEND

I'm just getting started with Talend and I would like to know how to divide a value from a CSV file and round it if possible?
Here's my job layout:
And here's how my tMap is configured:
I assume the "/r" is to add a new line? That won't actually work and will instead add a string literal "/r" to whatever other string you're adding it to. You also don't need to do that because Talend will automatically start a new line at the end of the row of data for your tFileOutputDelimited.
But more importantly, you're attempting to call the divide method on a string which obviously doesn't exist (how would it be defined?).
You need to first parse the string as a numeric type (such as float/double/Big Decimal) and then divide by another numeric type (your Var1 is defined as a string in your example, so will actually fail there too because a string must be contained in quotes).
So typically you would either define the schema column that you are dividing as a numeric type (as mentioned) or you'd attempt to parse the string into a float in the tMap/tJavaRow component.
If you have your prices defined as something like a double before your tMap/tJavaRow operation that divides then you can use:
row1.prix2 / Var.var1
Or to round it to two decimal places:
(double)Math.round((row1.prix2 / Var.var1) * 100) / 100
You can also use a tConvertType component to explicitly convert between types where available. Alternatively you could parse the string as a double using:
Double.parseDouble(row1.prix2)
And then proceed to use that as previously described.
In your case though (according to your comment on Gabriele's answer), there is a further issue in that Java (and most programming languages) expect numbers to be formatted with a . for the decimal point. You need to add a pre-processing step to be able to parse your string as a double.
As this question's answers show, there are a couple of options. You can use a regex processing step to change all of your commas in that field to periods or you can use a tJavaRow to set your locale to French as you parse the double like so:
NumberFormat format = NumberFormat.getInstance(Locale.FRENCH);
Number number = format.parse(input_row.prix2);
double d = number.doubleValue();
output_row.nom = input_row.nom;
output_row.code = input_row.code;
output_row.date = input_row.date;
output_row.ref = input_row.ref;
output_row.ean = input_row.ean;
output_row.quantitie = input_row.quantitie;
output_row.prix1 = input_row.prix1;
output_row.prix2 = d;
And make sure to import the relevant libraries in the Advanced Settings tab of the tJavaRow component:
import java.text.NumberFormat;
import java.util.Locale;
Your output schema for the tJavaRow should be the same as the input but with prix2 being a double rather than a string.
Since var1 is defined as String you cannot apply the divide method. Try something like this for your output prix2 calculus:
(Float.parseFloat(row1.prix2)/2200f) + "Vr"
or something like that (I cannot read the text in the screenshot very well, actually)

Java Decimal Format - as much precision as given

I'm working with DecimalFormat, I want to be able to read and write decimals with as much precision as given (I'm converting to BigDecimal).
Essentially, I want a DecimalFormat which enforces the following pattern "\d+(\.\d+)?" i.e. "at least one digit then, optionally, a decimal separator followed by at least one digit".
I'm struggling to be able to implement this using DecimalFormat, I've tried several patterns but they seem to enforced fixed number of digits.
I'm open to alternative ways of achieving this too.
Edit:
For a little more background, I'm parsing user-supplied data in which decimals could be formatted in any way, and possibly not in the locale format. I'm hoping to let them supply a decimal format string which I can use the parse the data.
Since you noted in a comment that you need Locale support:
Locale locale = //get this from somewhere else
DecimalFormat df = new DecimalFormat();
df.setDecimalFormatSymbols(new DecimalFormatSymbols(locale));
df.setMaximumFractionDigits(Integer.MAX_VALUE);
df.setMinimumFractionDigits(1);
df.setParseBigDecimal(true);
And then parse.
This seems to work fine:
public static void main(String[] args) throws Exception{
DecimalFormat f = new DecimalFormat("0.#");
f.setParseBigDecimal(true);
f.setDecimalFormatSymbols(new DecimalFormatSymbols(Locale.US));// if required
System.out.println(f.parse("1.0")); // 1.0
System.out.println(f.parse("1")); // 1
System.out.println(f.parse("1.1")); // 1.1
System.out.println(f.parse("1.123")); // 1.123
System.out.println(f.parse("1.")); // 1
System.out.println(f.parse(".01")); // 0.01
}
Except for the last two that violate your "at least one digit" requirement. You may have to check that separately using a regex if it's really important.

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