The compiler prevents you from using a potentially null variable, unless you check it is not null. Ie. it forces you to check a potentially null value before using it. The type system is strict, but flexible, allowing union and intersection of types, covariant and contravariant types, reified types, etc. Type inference and union types allows a dynamic programming style, close of JS spirit.
Ranked in these QuestionsQuestion Ranking
Pro Strongly typed, good tooling
That's Java, so it is strongly typed, and we can use fully the IDE: error detection, refactoring, auto-completion, etc.
Produced JS is highly optimized, can be separated in modules with lazy loading, can be internationalized while loading only the chosen language.
Pro Familiar for Java developers
Perfect if you have a strong background in Java programming, and need to code for the client side.
Pro Fantastic IDEs
Because Java is statically typed, integrated development environments (IDEs) for Java can provide a lot more feedback on errors you will encounter. Java IDEs can give you specific errors in the location where they occur without having to run the code every time. This makes is faster to debug and learn from your mistakes.
IDEs also have extensive auto complete capabilities that can help you learn the programming libraries you are using faster and tell you what functions are available.
Pro Most commonly used language in industry
Pro Consistent programming standards
Most Java code follows very standardized coding styles. This means that when you're starting out, there are fewer questions about how you should implement something as the programming styles and patterns are well established and consistent. This consistent style means that it's often easier to follow others' example code, and that it's more likely to meet at least a certain minimum standard of quality. This discipline with consistent stylistic standards also becomes useful later, when collaborating on projects with larger teams.
Pro Strong static typing, null safe and flexible, almost dynamic type system
The compiler prevents you from using a potentially null variable, unless you check it is not null. Ie. it forces you to check a potentially null value before using it.
The type system is strict, but flexible, allowing union and intersection of types, covariant and contravariant types, reified types, etc.
Type inference and union types allows a dynamic programming style, close of JS spirit.
It brings type safety to JS, allowing to define interfaces to existing JS APIs, yet using the
dynamic keyword for flexible calls in the JS ecosystem.
Pro Excellent IDE support
Ceylon has reified generics, so it doesn't loose the type of collections at runtime. This makes autocompletion, debugging, etc. first-class. The Eclipse plugin makes it a full-fledged Ceylon IDE, and an IntelliJ IDEA plugin is in the works.
Pro Great tutorial
Gavin King, main author of the language, has a great, clear technical writing style, making understandable difficult concepts like variance or sound type system.
Pro Try it out in the browser
It has a Web IDE: http://try.ceylon-lang.org/ with impressive demos: http://try.ceylon-lang.org/?gist=bd41b47f325b6d32514a so you can try it without installing anything, and see the JS generation / interop in action.
Pro Excellent documentation
The language specification is very complete and up to date; also, the language module is very well documented.
Pro Easy to learn even if you don't have prior programming experience
Ceylon is indeed fairly easy and readable. Of course those ones who know OOP and a bit of functional programming concepts will feel almost at home right from the start.
Pro Generate HTML
HTML generation is supported right in the SDK.
Pro Same code in backend and frontend
Con Too verbose
- A Hello world needs package, class, static method and the actual
- Reading a line from input requires instatiating 5 objects in the right order.
- Exceptions are everywhere, particularly since all values are nullable.
- Java has a getter/setter culture, but without native syntax support.
- portable Java code lacks anonymous functions, and continues to lack good support for partial application, compensating instead with verbose design patterns, kludges like anonymous inner classes, or just inline code.
- It is statically typed without type inference, with a culture that promotes long class names.
- Poor support for sum-types and pattern matching leads to overuse of inheritance for dynamic dispatch and chains of nested conditionals
Especially for beginners, this can make reading Java code feel overwhelming; most Java courses tell students to simply copy, paste, and ignore a significant percentage of the code until they've learned enough to understand what it means.
For experienced programmers, this makes Java feel tedious, especially without an IDE, and actively discourages some solutions and some forms of abstraction.
Con Lack of physical or electronic books
We should hope Red Hat or anyone interested would take the time and write one. That would strengthen the maturity of the language, but Ceylon is rapidly developing which can make the author's efforts futile because his or hers work will become obsolete soon.
The second hindrance is, of course, popularity of the language which can't give much to the pockets of the author (however, Dart's unpopularity at start didn't prevent it to have a lot of printed material, but that's Google's child, we know).
Con Currently has large runtime
Ceylon 1.2 needs a language runtime of 1.55 MiB, and the Collection library adds another 370 KiB. That's a lot for the Web...
Now, this has to be put in perspective: if you use Ceylon to make a web application, these files will be loaded once, then cached by the browser (that's not casual browsing).
Moreover, most servers compress such resource, and the numbers become respectively 234 KiB and 54 KiB, which is more reasonable...