Freemarker Default Number Formatting

We use Freemarker quite extensively at Betfair, and a question was raised the other day by one of the developers regarding number formatting. He had a numeric value that was being rendered with thousand separators and it wasn’t immediately obvious why. He quite rightly assumed that Freemarker would write the value of the number – unformatted – in the output. After all, this is the default behaviour of pretty much every other language / framework / tool that we use.

Unfortunately, Freemarker sees things differently. And this is where it’s REALLY important to make sure you read the documentation! Freemarker claims to be rendering for a “human audience” by default, but they’ve forgotten that Freemarker is a developer’s tool. Programmers are intelligent enough to know when they want numbers to be formatted. Automatically formatting numbers is not doing us a favour. Unless the programmer asks you to do something… don’t do it!

Scenarios like this can trip up anyone, and could possibly go unnoticed until something breaks in production. Let’s say for example that you were using a number as part of a link that you were rendering in the page. If all your testing used numbers smaller than 1000, you’d never see any problems. It’s only when you go over 1000 that the issue makes itself known. Our test data covers a large number of scenarios that quickly exposed this issue, but I can definitely think of smaller projects I’ve worked on in the past where this would not have been discovered early enough.

In fact, I think this default behaviour is dangerous. It breaks the Principle of Least Astonishment (or Principle of Least Surprise, as we call it). Not only that, but from what I can tell from the docs, it cannot be overridden. So there’s no way to change the default back to what is sensible.

Here’s an example of what happens when you render numbers using Freemarker and how to make sure you get the output you want. The example below assumes an English locale.

<#assign x = 1000>
${x}                 <#-- 1,000 -->
${x?string}          <#-- 1,000 -->
${x?c}               <#-- 1000 -->
${x?} <#-- 1000 -->

As you can see above, the default rendering of a number is formatted based on locale. If you simply want the raw number, you must explicitly specify that by using ? or use the shorthand notation ?c.

If you want more information on this, check out the docs.


Even Better Java i18n Pluralisation using ICU4J

Last week I wrote about Java’s built-in ChoiceFormat class and the support it provides for pluralisation. It is a very useful class, but as pointed out by two commenters (btw… thanks for the feedback!) it doesn’t cater well for all languages – particularly those that have more complex rules. This led me to investigate further, as I was certain there would be something useful out there – after all, internationalisation is a very common requirement of a large number of applications. After a little digging, I found that the one library that stands out is ICU4J. So who uses it? Well… pretty much everyone!

So for those that have more complex internationalisation requirements, this is an excellent library to use! I generally find that the best way to find out how something works is to see an example, so I’ve used the pluralisation example provided in the comments of my previous post to demonstrate ICU4J. I chose this example for a few reasons: firstly, because someone took the time to ask a question and I want to answer it; secondly, because it is clearly not supported by the JDK ChoiceFormat class; and lastly, because I only know languages with simple pluralisation rules.

I wrote a very basic class that simply prints out a localised message looked up from a ResourceBundle – which is probably the most commonly used approach and therefore familiar to most readers.


import java.util.Locale;
import java.util.ResourceBundle;

public class IcuDemo {

    private static final int[] NUMBERS = new int[] {0, 1, 2, 5, 11, 22, 39};

    public static void main(String[] args) {
        printLocalisedMessages("plural", Locale.ENGLISH, new Locale("pl"));

    private static void printLocalisedMessages(String key, Locale... locales) {
        for (Locale locale : locales) {
            System.out.println(locale.getDisplayLanguage() + ":");
            printLocalisedMessage(key, locale);

    private static void printLocalisedMessage(String key, Locale locale) {
        ResourceBundle bundle = ResourceBundle.getBundle("icu", locale);
        String pattern = bundle.getString(key);
        MessageFormat msgFormat = new MessageFormat(pattern, locale);

        for (int i : NUMBERS) {
            System.out.println(msgFormat.format(new Object[] {i}));


The code above should be familiar to everyone, as it shouldn’t be all that different from how you’re already doing i18n. However, note that I’ve imported instead of the usual java.text.MessageFormat. The really interesting part comes in when we use ICU4J’s “plural” format type, which is shown in the following properties files:


plural={0} {0, plural, one{car}other{cars}}

plural={0} {0, plural, one{auto}few{auta}many{aut}other{aut}}

I’m sure you’ll immediately notice that I’m not specifying numbers in these patterns, as we did with ChoiceFormat. Instead, I’m simply referring to categories of numbers by predefined mnemonics. This really cool feature is available because a number of language pluralisation rules have already been defined by the Unicode CLDR (Common Locale Data Repository). In particular, we’re using the Language Plural Rules, which are provided in the ICU4J package. To explain how this works, let’s look at the English example and then work our way up to the Polish example.

English has two categories – singular/plural. These two categories are named as “one” and “other” – fairly straightforward. What this really means in terms of plural rule definition is:

one: n is 1
(by implication, every other number falls into the "other" category)

Polish is more complex than this and requires a number of rules to be defined:

one: n is 1
few: n mod 10 in 2..4 and n mod 100 not in 12..14
many: n is not 1 and n mod 10 in 0..1 or n mod 10 in 5..9 or n mod 100 in 12..14
(by implication, every other number falls into the "other" category)

Clearly the definition of rules makes our lives a lot easier. All we need to know is which category of numbers we want to provide a pluralisation for, and define the message against that name using the format “keyword{message}”.

Note: The CLDR points out that the names are just mnemonics and aren’t inteded to describe the exact contents of the category, so try not to focus too much on them. It’s merely providing categorisation by a recognisable name.

The above example only uses the predefined number categories, but we could easily mix this with explicit values if needed. In this case, the explicit values would be checked first for an exact match, and if none was found then the categories would be searched, and failing that the “other” category would be used. Here’s an example of how you can mix the two concepts together:

example={0, plural, =1{one}=5{five}other{#}}

If we formatted this with the numbers 1 to 5 in a loop, this would be formatted as follows:


Of course, there may be circumstances where the predefined rules don’t do what you want (although, we’re probably talking about exceptional circumstances now). In this case, you can simply define your own set of rules. This can be done using the PluralRules class or by customising the locale data that’s available to ICU4J.

I’ve only scratched the surface of what you can do with this library – and pluralisation is only one very small part of what it provides – but I hope this is useful and is able to help get you started using it.

Java i18n Pluralisation using ChoiceFormat

Betfair‘s site is hugely popular all around the world, and obviously needs to provide a fully localised experience for users across different locales. Yesterday I was looking at how best to provide internationalisation (i18n) support within our core platform and came across the really useful ChoiceFormat class. I had seen it before but hadn’t actually explored what it can do until now. It’s an extremely basic class in terms of the functionality it provides, but it is as powerful as it is simple.

I’m sure we all know about Java resource bundles for i18n and have probably used them quite a lot – so I won’t go into any detail on that. I’ll just assume it’s common ground. However, if you haven’t come across java.text.ChoiceFormat, you’re missing out! This is the guts of pluralisation within the i18n stable, and is definitely your friend when you realise that users don’t like messages that say “Updated 1 second(s) ago”. You know it’s 1 second, right? So why not just say that and skip the “(s)” bit? I’m sure many have tried to solve this the hard way by doing the intelligence themselves (defining multiple keys and choosing which to use based on the argument to be passed into it), but this is where ChoiceFormat comes into play.

As per the docs, “The choice is specified with an ascending list of doubles, where each item specifies a half-open interval up to the next item”. So let’s use the example above to show how it would be defined in a resource bundle:

lastUpdated=Updated {0} {0,choice,0#seconds|1#second|1&lt;seconds} ago

What this does is creates a bunch of contiguous ranges (in ascending order) and finds the best match. I said best match because sometimes there isn’t an exact match. In the example above, negative numbers don’t match any range – but because they’re smaller than the starting range, the first choice is selected. The same logic applies for values that are larger than the highest range (which isn’t possible in this example as the highest range ends at positive infinity).

So let’s run through the scenarios very quickly:

  • If you pass in a negative number, the first choice “seconds” is returned (because it is too small to match anything and the ranges work in ascending order)
  • If you pass in a number between 0 (inclusive) and 1 (exclusive), the first choice matches and “seconds” is returned
  • If you pass in number 1 (exactly), the second choice matches and “second” is returned
  • If you pass in a number greater than 1, the last choice matches and “seconds” is returned

You may have noticed that the definition is different for the last range. What this is effectively doing in code is calling ChoiceFormat.nextDouble(1) which returns the smallest double greater than 1, which is then used as the start of the range. This is not restricted to being used the last range, but can actually be used anywhere. There is a similar ChoiceFormat.previousDouble(double d) that is fairly self-explanatory.

Nifty! Even more so when you consider that some languages have multiple pluralisations to consider (e.g. Russian). So you can’t reasonably assume that you’re always dealing with a simple singular/plural as we have in English – sometimes there are many different plurals to take into account.

Bug in Java 6 DecimalFormat.format()

While trying out some options for decimal formatting, I came across what appears to be a bug in Java 6. I haven’t yet traced back exactly which version introduced the bug, but I have managed to verify it on both Windows 7 running Java 6 Update 23 & 24 and on Mac OS X Snow Leopard running Java 6 Update 26.

According to the JavaDocs for java.text.DecimalFormat:

If there is an explicit negative subpattern, it serves only to specify the negative prefix and suffix; the number of digits, minimal digits, and other characteristics are all the same as the positive pattern. That means that “#,##0.0#;(#)” produces precisely the same behavior as “#,##0.0#;(#,##0.0#)”.

However, when putting this into practice, the formatter truncates the final character from the output. This is shown in the following JUnit test:

public void testDecimalFormat() {
  double value = -4000d;

  final String expected = "(4,000.00)";
  final String actualA = new DecimalFormat("#,##0.00;(#,##0.00)").format(value);
  final String actualB = new DecimalFormat("#,##0.00;(#)").format(value);

  // passes
  assertEquals(expected, actualA);

  // fails - actualB = "(4,000.00"
  assertEquals(expected, actualB);

I have logged this on the Java Bugs Database and will update this post once I have a response from Oracle. But hopefully this helps someone else that has come across the same issue.

UPDATE: Yes, it is a bug. You can track it here (may take a day or two to appear on the external bug database apparently).

Common Misconceptions about Web Performance Optimisation

What would you do to improve the performance of a web application?

This is a question I’ve posed to a fair number of Java developers in the past week. A common theme quickly emerged and remained consistent across all the responses, which is that everyone I spoke to immediately began listing improvements to the server-side processing involved in a typical page request. Many of the responses were perfectly valid and often considered “best practice” (as much as I can’t stand that term), but few were likely to have much of a noticeable impact to the user. Some even mentioned the use of caching, but only thought to apply it internally within the server (e.g. database cache) and not to the content within the response.

It seems that the natural assumption of many Java developers is to look for optimisations in their code before trying to understand the entire request-response lifecycle and all the actors involved. According to Steve Souders, “80-90% of the time spent by users waiting for pages to load is spent on the frontend”. If that comes as a shock to you, then I strongly recommend that you read High Performance Web Sites. It is an excellent reminder of the obvious, but often forgotten, reality that your website is accessed by people, using browsers, across networks and domains, via intermediaries (proxies, etc.), over a common protocol (HTTP).

Digging into each of the bolded items above will give a much better appreciation of the components that act in concert to provide a web experience to the user. If this is the first you’ve heard of web performance optimisation and you want to know more, I recommend the following sites:

Steve Souders’ 14 Rules for Faster-Loading Websites (from his book, High Performance Websites)

Yahoo!’s Best Practices for Speeding Up Your Website

So next time someone asks you that question, please throw in a few optimisations other than server-side processing.

Certification and Competence

I found it quite interesting reading Martin Fowler’s recent post about the correlation between certification and competence, especially so recently after writing about the changes to some of Oracle’s certifications!

I have to say that I completely agree with his opinion – and I know it’s shared by most (if not all) of my friends. Having earned a number of certifications over the course of my career, I have seen first-hand just how useless so many of them are. I must emphasise that this is not necessarily true of all certifications. However, from my experience, none have proven enough to establish the holder of the certification to be an expert on the subject – and this is really where they fail.

So why did I decide to take on the Java Enterprise Architect certification? Well, I approached my investigation of it with the usual skepticism, but was finally convinced by one major aspect: it is ultimately assessed by a human being! As Fowler points out:

“At the moment the only way you can tell if someone is a good programmer is to find other good programmers to assess their ability.”

I don’t like certifications that are comprised of nothing by MCQ’s – not enough can be tested in a few multiple choice questions to be able to certify someone as mediocre, let alone an expert! Unless the candidate has had to form an opinion and defend it, you haven’t really tested their ability to apply their knowledge and reasoning. You’ve just asked them to regurgitate simple facts. At best, you’ve tested their ability to recognise a solution to a particular problem – but you haven’t established whether, given a blank sheet of paper, they are able to come to the solution themselves.

I’m hoping that the Java Enterprise Architect certification is able to distinguish the competent from the incompetent, but at this stage I’m not sure. I do know one thing though… adding a course attendance requirement does not strengthen the certification. Unfortunately, I feel this is where the “good money-making opportunity” that Fowler mentions comes into play.

Changes to Oracle Certification for Java Architects

I’ve recently completed the first exam towards the Oracle Certified Master, Java EE 5 Enterprise Architect and had aimed to complete the assignment later this year. However, I just happened to go to the Oracle Certification website where I saw that the rules are changing for a few of their certifications.

Quoted from the announcement on their website:

Beginning August 1, 2011, Java Architect, Java Developer, Solaris System Administrator and Solaris Security Administrator certification path requirements will include a new mandatory course attendance requirement.

I can’t say I’m impressed with how quietly they announced this! I haven’t seen anything on the OTN Java site about it, nor have I seen any attempt to make developers aware of this through other channels. I also have not received any emails from them about the changes to a certification track that I am currently working on. Unless I’ve managed to miss the announcement somewhere, I can only guess that they’re trying to sneak this in quietly to get more money out of us. Perhaps I’m being a bit cynical, but I don’t think it’s too far from the truth, given Oracle’s recent track record with the Java community.

So if you’re busy working towards any of these certifications, I suggest you pick up the pace and get it done by the end of July! And here I thought things were starting to settle down.

Fortunately the certification assignment has a very similar focus to my next assignment at Oxford. If all goes well, I might just manage to get it done in time.