I asked a question How to get an Integer as result?
The suggested solution with decimalFormat works, but my problem is that I want my data not only to be presented as ##.0 but to be like this, because in the end of my program I use them. So I want to be exactly in that type; otherwise I get the wrong final number. Any ideas?
EDIT:
let me be more specific. i get 12,344 from my first calc, 14,4566 from my second and 18,5644 from my third.that makes a sum 45.365.Now,if i do then 12,3 , 14,4 and 18,5 the sum is 45.2...thats the point of my answer.i want to have 45.365 at the end and not 45.2
The problem seems to be a design issue with your app.
On the one hand, you want to display the results to the user with 1 digit after the decimal point.
In the other hand, you actually want to keep the extra precision and use it for follow-up calculations.
I would argue that this is a poor user interface model. IMO, the numbers that the user sees should be the numbers that go into the calculations. This means you should either:
show the user more digits after the DP in the first place (or at least give a visual indication that there are more digits), or
do the calculations using the rounded / truncated values ... as displayed to the user.
Once you have figured out a consistent user interface model, the required implementation approach should be much clearer to you.
Related
I have an object from an implemented class ReportManager. Now getReport() is a number like 0.23 with the data type report. But I want this number to be a double so I can work with it.
I cannot change the class, because it is implemented in the Java compiler (it is for writing macros for a program).
Does anybody have a suggestion how I could handle it? I checked the API and there is no function implemented that could help me.
EDIT: I do have the situation: I want to calculate the Center of Pressure of an object in my simulation. So I need the moment in that position to be 0.
Now: This is how the automated macro ask the value of the Moment:
MomentReport momentReport_0 =
((MomentReport) simulation_0.getReportManager().getReport("Moment 1"));
Now I want to take the abs of it, because I don't mind if it's positive or negative.
while(Math.abs(momentReport_0) > 0.2)
(Do iterate and change position.) At the end I want to println the the position.
simulation_0 is an object of Simulation. I could copy a part of the API if it's needed. Just don't know which class documentation would help.
You can cast the number to a double so that you can work with it, assuming it's returning you a single-precision float at the moment.
double result = (double) reportManager.getReport();
I recommend you read up on what typecasting is so that you can better understand what's going on here, as there would be some situations where it's unsafe to cast:
https://en.wikipedia.org/wiki/Type_conversion
for some reason I found myself coding some piece of software, that should be able to perfom some astronomic calculations.
While most of it will be about transfering the correct formula into Java, I found an annoying Problem right at the verry beginning of my "test how to calculate big numbers".
Well... Imagine the Sun (our Sun), which has a mass of (about and rounded, for more easy explaining) 10E30 kg. Ten with 30 following Zeros. All native datatypes are just unusuable for this. To mention: I KNOW that I could use 3000 to calculate things and just add trailing zeros in the output-view, but I hoped to keep it as precise as possible. So using short numbers will be my last resort only.
Comming to the Problem. Please have a look at the code:
BigDecimal combinedMass = new BigDecimal(1E22);
int massDistribution = 10;
Integer mD1 = massDistribution;
Integer mD2 = 100 - massDistribution;
BigDecimal starMass;
BigDecimal systemMass;
systemMass = combinedMass.divide(new BigDecimal("100")).multiply(new BigDecimal(mD1.toString()));
starMass = combinedMass.divide(new BigDecimal("100")).multiply(new BigDecimal(mD2.toString()));
System.out.println((systemMass).toEngineeringString());
System.out.println((starMass));
It will output 1000000000000000000000 and 9000000000000000000000, whats exactly what I did expect. But look at the combineMass Field. If I raise it to 1E23, the Output will change
I get 9999999999999999161139.20 and 89999999999999992450252.80...
So I know I could use jut BigInteger, because its more reliable in this case, but for the sake of precicion, sometimes the BigWhatEver may drop to something like 50.1258
Plus, I hope to get the 10.xE30 as output, whats only possible using bigDecimals.
I want to know: Is there no way avoidng this (that error appers above 1E23 for every value I tried), while keeping the ability to calculate Floating-Points? Should I cut the After-Decimal-Separator-Values for this Field to two digets?
And for something more to wonder about:
System.out.println(combinedMass.precision());
in relation with the code above will provide 23 for that case, but En+1 for most other values (Thats was when I grow really confused)
Thanks for advise.
You're using basic types without realizing it:
new BigDecimal(1E22);
Here, 1E22 is a primitive double, and you already lost precision by using it.
What you want is
new BigDecimal("10000000000000000000000");
or
new BigDecimal(10).pow(22);
System.out.println("Hello all that use Java && JFreeChart!");
I am writing an application that allows cyclists, such as myself, to keep track of their average speed, distance, and time for a given trip. They are to enter that data, and then a JFrame pops up with their graphed information. I have a class that converts the elapsedTime to a String format (for display purposes!), but I don't think JFreeChart can take it in for a Range value. In fact, I checked out their API documentation, http://www.jfree.org/jfreechart/api/javadoc/index.html , and quickly found out that Range() only takes parameters of type double! Not String, not Time, double. This is a letdown because I intended to set the interval of graph displayed equal to the interval formed by their minimum time and maximum time. Is there any way around this?
From my understanding of the question, you could try:
double value = Double.parseDouble(string);
However, this will obviously not work if you put in a time-based value. From the comments you have made, perhaps a TimeSeriesChart from ChartFactory could solve your problem.
It seems like the ChartFactory.createTimeSeriesChart() is the way to go, but it is the most disappointing way to go. Sure, you can switch the axes, but this does NOTHING to the data! The smartest way to approach this would be an XYLineChart, and then use a RelativeDateFormat : http://www.jfree.org/jfreechart/api/javadoc/index.html . That way, your range values go in as type long, and then you can just bring in a DateAxis that has RelativeDateFormat. Problem solved.
I think I'm facing a paradox here.
What I'm trying to do is when I receive/make a call, I have the number, so I need to know if its an international number, if its a local number, etc.
The problem is:
For me to know if a number is international, I need to parse it and check its length, but, the length differs from country to country, so, should I do a method that parses and recognizes for each country? (Unfunctional in my opinion);
For me to know if its a local number, I need the area code, so I have to make the same thing, parse the number and check the lenght, get the first numbers based on the area code lenght;
Its kinda hard to find the solution for this. The library libphonenumber offers a lot of usefull classes, but the one that I thought that could help me, took me to another paradox.
The method phoneUtil.parse(number, countryAcronym) returns the number with its country code, but what it does is, if I pass the number with the acronym "US" it return the number with country code '1', now if I change the acronym to "BR" it changes the number and return '55' that is the country code for Brazil. So, anyways, I need the country acronym based on the number I get.
EX:
numberReturned = phoneUtil.parse(phoneNumber, "US");
phoneUtil.format(numberReturned, PhoneNumberFormat.INTERNATIONAL);
The above code, returns the number with the US country code but now if I change the "US" to any other country acronym it will return the same number but with the country code of that country.
I know that this lib is not supposed to guess from which country the number is (THAT WOULD BE AWESOME!!), but thats what I need.
This is really making my mind goes crazy. I need good advices from the wise mages of SO.
If you please could help me with a good decision, I'd be so thankfull.
Thanks.
PS: If you already use libphonenumber and has more experience with this, please guide me on which class to use, if there is one capable of solving this problem. =)
1) The second parameter to phoneUtil.parse must match the country you're currently in - it's used if the phone number received does not include an international prefix. That's why you get different results when you change the parameter: the phone number you pass it does not contain such a prefix, so it just uses what you've told it.
Any parsing solution set to determine if the phone number is international or not will need to be aware of this: depending on the source, even a national number may be represented with the international dialing prefix (usually abstracted as +, since it differs between countries, but this is not guaranteed).
2) For area code parsing, there is no universal standard; some countries don't use them, and even within a country, area codes may have differing lengths (e.g. Germany). I'm not aware of an international library for this - and a quick search doesn't find anything (though that doesn't mean one does not exist). You might need to roll your own here; if you only need to support a single country, this shouldn't be too hard.
I want to create a program for generating the series for the given base-n. ,
for example if my input is 2,then series shuould be, 00,01,10,11,etc.,(binary)
if my input is 10,then series shuould be,1,2,3,4,5,etc.,(decimal)
is there any general mechanism to find these numbers so that I can program for base-n.,
UPDATE:-
After,working out.,i face issue.
If I want to process that integer how to do that? Some body commented that, BaseInteger class I should use. please elaborate
You could use Integer's toString(int i, int radix) method for that.
For example:
Integer.toString(2, 2) // number 2, base 2
returns the string:
"10"
Note that the radix should be between 1 and 36.
You might be looking for something like this (take a peek at "Algorithm: Constructing Base b
Expansions"):
https://docs.google.com/viewer?url=http://websupport1.citytech.cuny.edu/faculty/dkahrobaei/Integers%2520and%2520Algorithms.pdf
I think you should first figure in which format you need the results. If they should be Strings, Bart's answer would probably suit you. An integer representation, which does actually mean something else (e.g. the int 10 does mean 2 with base 2) seems awkward to me. If i would need something like you described, i would probably implement a BaseNumber class first.