I have an application written in C++ (makes heavy use of templates) that I need to take to the Java ME platform.
I have two questions:
Are there any good tools to convert C++ code to Java - do some basic stuff so I have a platform to start with. I found this - http://tangiblesoftwaresolutions.com/Product_Details/CPlusPlus_to_Java_Converter_Details.html. It would at least eliminate the need for simple but time-consuming stuff like moving classes to different files, namespaces to packages, etc. Has anyone tried it? Or knows of any better ones?
The bigger problem is how to deal with templates - the code makes very heavy use of them. Any suggestions on how to go about this? Are there any tools to expand templates for instance so I have a rudimentary base and then I could work on writing the modules in Java?
Any help would be appreciated.
For all of Sun's marketing, Java is not simply a better C++, and in fact does not support many of the idioms and paradigms C++ supports. This makes automated translation difficult. How should you automatically turn a multi-inheritance hierarchy into Java's single inheritance hierarchy? (Note, I am not saying that a multi-inheritance hierarchy is a good thing, only that it is explicitly allowed in C++). More fundamentally, how would you represent a pointer-to-member function in Java? Or handle the differences between Java and C++ overload resolution?
Java added generics a few years ago, but purposely made them less powerful than C++ templates. Regardless of whether that was a good idea, it limits what automated translation can do with heavily templatized code.
Aside from using some research compiler that can turn C++ into Java bytecode, I'm afraid you may be stuck doing the translation by hand.
Can you use JNI and call the old C++ code from the new Java code?
I think for your case a very simple tool would be possible and perhaps worthwhile. Might be a fun weekend-job, though! A friend of mine once did a port from C++ to Java and he just made a list of regular expression substitutions. Like, he had all occurrences of -> replaced by a dot. And so forth. This was some years ago, however, so I don't really feel like asking him.
So, you could do the same, collect some easy substitutions and perhaps publish them somewhere on github?
Generics is the Java feature that corresponds to C++ templates and they are not supported in J2ME. You can use them with the aid of a framework, which probably uses pre-processing to do the trick. (Actually Generics in Java is a compiler feature - the JVM knows nothing about them.)
Anyway, it will be difficult if not impossible to automatically port even a small portion of your code form C++ to Java Standard Edition - things are much worse with J2ME. There are many and important differences between Java Generics and C++ templates.
I don't think it's going to be possible, esp. if your original code is heavily templatized - J2ME doesn't support generics, AFAIK.
Unfortunately, it seems like this will require a lot of manual work to go through the original code and rewrite it (I'm assuming your target platform doesn't support JNI)
Related
I'm a big fan of functional programming languages (namely Standard ML and its dialects), mainly because of their expressiveness which allows for very consise, clean code. I can solve many problems dramatically faster with ML than with say Java.
However, Java is really great when it comes to programming GUIs (->SWT). I would definitely not wanna do that in a functional language.
This brings us to my actual question: Is there a good way to write a program in ML and then wrap it with a GUI written in Java?
What I have come up with so far is the following:
Compile the ML programm (e.g. with MLton or Poly ML) and execute the binary as
an external program from Java
(http://www.rgagnon.com/javadetails/java-0014.html).
Problem: The only way the Frontend/Backend can communicate is via Strings. This might require tons of (difficult) encoding/decoding.
Use JNI/JNA. From what I read, this will allow you to transfer Integers, Arrays etc. I think the external programms have to be written in C/C++ for this to work. With MLton's Foreign Function Interface I can write an Interface to my functional program in C and statically link the whole thing.
Problem: Apparantly, this only works with dynamic libraries, that is dlls in Windows. However, MLton will only let me compile the ML/C Programm to an executable. When trying to create a dll, I get a whole bunch of errors.
Does anyone have experience with this? Is there a better way to do this?
Thanks in advance! -Steffen
EDIT: I know about Scala which tries to bring concepts from functional programming to Java. I have tried it but I dont think it can compete with an actual functional programming language (in terms of expressivness)
That's not quite the exact answer but there is a functional language which is very ml-orientated for the JVM: Yeti
So if you like coding in ML than that's probably currently the closes you can get on the JVM and it integrates of course very well with all the Java APIs.
Is there a good way to write a program in ML and then wrap it with a GUI written in Java?
I don't know if this is a good way for small applications, but it is definitely a way, one that works for big IDE style stuff: Isabelle/ML vs. Isabelle/Scala/JVM. This is an application of interactive theorem proving, but plain SML programming is a trivial instance of that, in a sense.
So you can write basic Isabelle/ML code that emits some messages in the manner of the old-fashioned REPL, but the output can be interpreted by GUI components on the JVM side. Isabelle/jEdit does that routinely for pretty-printing of colored text, with a tiny little bit of rich text (sub/superscripts and bold).
Concerning explicit recoding of functional values over pipes/sockets as strings: that turns out quite simple in Isabelle/ML/Scala, due to some imitation of the way SML would represent typed values in untyped memory, but using untyped XML trees here instead of bits. The XML transfer syntax is specific to keep things simple: YXML instead of official quasi-human-readable XML. All of that fits into approx. 8000 bytes of SML source -- I am tempted to post the sources here, but better search the web for "Isabelle YXML" or "YXML PIDE".
Since Scala/JVM alone has been mentioned as standalone alternative: it definitely works, Scala is also very powerful and flexibile in imitating many programming styles (higher-order functional-object oriented), but for sophisticated symbolic applications like theorem proving, it just won't reach the purity and stability of SML. (Note that the underlying SML platform here is Poly/ML.)
I may be posting a premature question, and maybe I'm just freaking out for no reason, but the way Oracle is handling Java is not very promising. I am a nerd who fell in love with Java from the first sight, and use it all the time in my personal/freelance projects but now I am thinking of a replacement.
I am fluent in C#/VB.NET too but I am looking for something more like:
Open Source
Compiled
Cross-Platform
Object Oriented
Large standard library
Extensive documentation
Web development is a major plus
I was thinking about a compromise: Python/Django for web development (or PHP), and Qt for thick client development. Anyone with better thoughts?
Not so long ago, I decided to explore away from the JVM. I set foot on python, and even though i'm nowhere near the expert/ guru level, I dont regret it. Didn't choose C# (considered it) because I consider it to be more of the same. I alredy know (and like a lot) C++, so python seemed like something new, which is what I was looking for.
It fullfils many of your requirements. Particularly, i'm decided not to learn PHP, so the web frameworks in python came in great.
Not to mention, Python has a large community (also see here), always eager to help and teach, which I consider to be very important.
Just my two cents.
Might be worth loking at the other JVM languages - Clojure and Scala are the two I personally think are most promising.
Yes you are on the JVM, but you're pretty independent from Java the langauage and don't have to use any Sun/Oracle implementations if you don't want to.
Having said that - I think that you are worrying a little too much about Java, too many players (including Oracle!) have too much invested to let it go too far off course.
Try Scala. It looks extremely elegant and promising. Being object oriented and sharing a lot with java in a very concise manner.
Everything you said points to C#, except for the Open Source point.
To fix that, there's Mono.
You could try D. My one-sentence description of why it's an awesome language is that its generic programming/compile-time introspection/template metaprogramming facilities are good enough to give you almost flexibility of a duck-typed language, while its execution speed and static type checking rival or exceed C++ and C#.
I think it meets your requirements quite well.
Open source: The frontend to the reference DMD implementation is open source (the back end isn't due to restrictions beyond the author's control). Work is underway to glue the reference frontend to open source backends such as LLVM (LDC) and GCC (GDC). In the case of D1 (the older version of the language) the LLVM port is fairly mature.
Compiled: D is meant to be compiled to native machine code, i.e. raw, inscrutable hexadecimal numbers.
Cross-platform: The reference DMD compiler supports x86 Windows, Linux, Mac OS X and FreeBSD. GDC and LDC will likely support a lot more CPU architectures.
Object oriented: D isn't a "pure" OO language in the Ruby sense of everything being an object, or in the Java sense of not supporting any other paradigm. It does, however, fully support Java-style OO as a subset of the language, along with procedural and functional style programming.
Large standard library: D1 has Tango, which qualifies. D2 has Phobos, which is not "large" yet by modern standards but is larger than C or C++'s standard lib. However, recently there has been a large interest in contributing and Andrei Alexandrescu (its main designer) has accepted several new contributors, including myself.
Extensive documentation: The standard library and language are reasonably well documented at the Digital Mars website. There's also Andrei Alexandrescu's book "The D Programming Language".
Web development: This is an admitted weakness. D doesn't (yet) have a good web framework, though its native unicode support and excellent generic programming support should make writing one relatively easy.
I too would like another Java-like technology to come along. Lately I've been doing Flex/Actionscript. While I really enjoy it, Actionscript technology seriously lacks the elegance that Java has. Adobe can write some good cross platform APIs, but they just don't have the head capital to build elegant languages and compilers. I've also tried Ruby, but the VM for Ruby is really bad. I've gone back to Java after my flirtation with other technologies and I think it's because the language is good enough, but the JVM is by far the best out there.
So do you want to stay with the JVM or do you really want to the leave the JVM altogether? Staying on the JVM there are lots of options: JRuby, Scala, Groovy, Javascript, Clojure are the big players. However, there are tons of great languages that can take advantage of the JVM's features.
Leaving the JVM there are still good options like python, ruby, and erlang. But you give up some of the nice features of the JVM like performance (big one), and the ability to drop down to a nice language like Java if you need speed. Those others mean using C or nothing at all.
I finally stopped worrying about Java's future. Sun did all it could to screw it up and it still turned out pretty darn good. I think Opensource has a lot more influence over Java's success than Oracle or Sun could ever have had.
I can't post comments yet, so I'm posting an answer related to the Python discussion. Though Python isn't compiled to machine code, there is a Python-to-C compiler called Cython, which can compile nearly all valid Python -- closures are finally (!) in the latest development release. It's have a big impact on some parts of the Python commmunity, e.g., I was at Euroscipy recently, and over half the talks mentioned Cython.
I personally don't like PHP, but it does meet all of your requirements. It doesn't officially support compilation but there is the Hip Hop project which compiles PHP to C code. Facebook is currently heading up this project.
That said, I highly discourage you from using it :)
C# is the only thing that will meet your needs and not feel hopelessly archaic, or frustrate with limited library. For open source/non-windows, use mono. It's a good, mature implementation of most of what's important in the CLR.
Some things (WPF, WCF, etc) are "missing" from mono, but these aren't so much part of the platform as they are windows-specific proprietary toolkits. Some of them are being implemented slowly in mono, some aren't. Coming from java you won't miss them because you're looking for a platform and good standard libraries to build upon, not a gui toolkit or whiz-bang communication framework.
As far as a platform to build stuff with that's "like" java and offers similar levels of functionality, C# + CLR is the clearest option.
Using also Cython you get the best of the two worlds , the ability to code in python , the ability to code in C and C++ and of course compile your code and the ability to use both python a c/c++ libraries out of the box. And if you dont like C++ syntax , cython syntax is python syntax and more.
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Is it possible for a developer to use Scala without knowing Java?
Is it possible for a developer to use Clojure without knowing Java?
Note: For example I am a C# developer and I use .NET without knowing any VB (Of-course WF 4.0 uses VB for statements, so I refuse any projects involving WF 4.0 :) ).
Summary I: Thanks to all for your answers. Now I can tell one can use these languages without knowing Java (The Language). Now I've got another question: How can one start with Java (JVM) ecosystem? What are beginner, intermediate and advanced knowledge-bases (bags!)? To be honest Java ecosystem was always a bit confusing to me, so it would be very helpful to provide some "reference references" and "defacto tutorials" for learning (curve!) JVM.
(OK! I will post it as another question!)
Scala, and Clojure even more so, are totally different languages from Java. The only thing they have in common is that they run on the Java virtual machine. You do not need to know the Java programming language to program in Scala or Clojure. It would be useful, however, to know something about the Java ecosystem (the Java virtual machine and runtime environment).
Sure you can. You'll lack the knowledge of the standard library at first, but that's not a big problem when you're starting with a new languages anyway. Clojure & Scala, however, put a heavy emphasis on the Java interop and do not try to hide the raw Java stuff, so you'd probably have to learn more about Java(not the language - the Java Platform) at some point to make maximum use of the language and the underlying platform.
Speaking from the perspective of knowing Java and Clojure (but not Scala), you can use Clojure just fine without knowing Java. You have access to the core language, which is fully-featured, and libraries (e.g. clojure-contrib).
However, one of the big benefits of using Clojure (versus other lisps) is access to the Java ecosystem - libraries, debuggers, JVM, etc.
So, yes you can use Clojure effectively and I wouldn't let a lack of Java knowledge hinder you, but you'll add to your bag of tricks if you eventually start to learn enough Java to take advantage.
Well, Clojure has been ported to the CLR. Probably easier thant the whole jump to the JVM since you are a .NET developer. :)
http://github.com/richhickey/clojure-clr
yes, thats me!
Has not been much of a problem for me except for when I needed a stupid simple swing gui. thats when I had to go back and review java.
Scala is totally different language than java. So yes, you can of course use scala without knowing java ( but of course you have to learn scala first). Even though, knowing java (or any OO language) + some functional language makes it easier to understand scala.
I am ActionScript 3/Flex programmer, it is the first language I learned.
I want to learn either Java or C++.
Would one of these be easier to learn based on my current knowledge?
It really depends what you want to do. C++ is more powerful and fast. But Java has a smaller learning curve.
I'd say learn C++, only because it will require you to gain a better understanding of how computers work under the hood. It will also help position you to learn Java, C#, or any other language down the road.
Java seems more likely to be directly relatable to your work in AS3; C++ is better for giving you a grounding in a different technology (pointer-style OO rather than object-style. C++ may feel eerily similar yet different).
If you are doing C-ish C++, the pointer language learning process can be very informative as to how OS-level calls are written...
The places where you will reach for one tool or the other are very different, and the use you have for the tool may be more important in deciding than their relative merits as languages - employability IS a use for a tool, after all.
Well, AS3 more closely resembles JavaScript - they both follow the ECMAScript specification.
But to answer your question, I would say learning Java will be more beneficial and easier for you. Java supports Interfaces, and single inheritance, like Flex, whereas C++ supports multiple inheritance and lacks a formal notion of Interfaces. Java and Flex both manage memory for you, whereas C++ forces you to manage your own memory. Both Java and Flex have large helper libraries out of the box, and both have native String types, whereas C++ forces you to find a library to use and doesn't support native String types.
This may be my own bias, but it also seems more likely that you'll find a job that is looking for a Flex/Java developer, rather than a Flex/C++ developer. Java and Flex seem to work well together, with Flex as a front end and Java as a middle and back end.
I would say Java is more similar to AS3 than C++. You will find lots of familiar metaphors and mechanisms.
C++ on the other hand, will require more effort to learn. It is closer to the machine and demands an undertanding of lower level mechanisms. For instance, there is no garbage collection so you have to manage your memory resources yourself.
Which is better to know depends on what you plan to do with the language. C++ is good at performance critical applications (games, all kinds of real time simulations etc.). Java makes it easier and safer to build things, but at the cost of performance.
hope this helps
regards
C++ is, generally, harder to learn than Java. You will find this true pretty much no matter what your previous experience. Therefore, if you want to learn the easier, learn Java.
(This is partly a matter of design philosophy. C++ was designed to be mostly upward compatible from C, at least the C at the time C++ was being designed. It was also designed
to be useful and permissive, with ease of learning being secondary. Java was designed partly as a reaction to C++, as a generally safer and easier language. C++ is more expressive than Java, but this comes at a price: it's harder to learn C++, and easier to screw up with it.)
That being said, you never said why you wanted to learn another language. You might well be better off learning C++, even though it is more difficult.
Whatever you'll finally decide to learn, do yourself a favor and read either Thinking in Java or Thinking in C++.
Both books are available - for free! - at Bruce Eckels website. They are very, very good.
C++ is more complex than Java so I'd suggest to take a look at Java, first.
However, this isn't meant as C++ bashing. Both are great language, it just depends on what you'd like to do in the end.
I would go with Java. It will be easier to learn and, given your background, I'm guessing you do more web/internet work in which case you'll probably find more ways to apply the Java knowledge then you would C++.
I think you would find Java more similar.
Learning C++ will likely require you to learn concepts that you could avoid with other high level languages (such Java and AS3) e.g. manual memory management, pointers, non forward looking compiler, multiple inheritance, etc.
This question already has answers here:
Where can I find a Java to C# converter? [closed]
(9 answers)
Closed 7 years ago.
Is there an effective tool to convert C# code to Java code?
I have never encountered a C#->Java conversion tool. The syntax would be easy enough, but the frameworks are dramatically different. Even if there were a tool, I would strongly advise against it. I have worked on several "migration" projects, and can't say emphatically enough that while conversion seems like a good choice, conversion projects always always always turn in to money pits. It's not a shortcut, what you end up with is code that is not readable, and doesn't take advantage of the target language. speaking from personal experience, assume that a rewrite is the cheaper option.
We have an application that we need to maintain in both C# and Java. Since we actively maintain this product, a one-time port wasn't an option. We investigated Net2Java and the Mainsoft tools, but neither met our requirements (Net2Java for lack of robustness and Mainsoft for cost and lack of source code conversion). We created our own tool called CS2J that runs as part of our nightly build script and does a very effective port of our C# code to Java. Right now it is precisely good enough to translate our application, but would have a long way to go before being considered a comprehensive tool. We've licensed the technology to a few parties with similar needs and we're toying with the idea of releasing it publicly, but our core business just keeps us too busy these days.
This blog post suggests useful results from Tangible.
There is a tool from Microsoft to convert java to C#. For the opposite direction take a look here and here. If this doesn't work out, it should not take too long to convert the source manually because C# and java are very similar,
These guys seem to have a solution for this, but I haven't tried yet. They also have a demo version of the converter.
Although this is an old-ish question, take a look at xmlVM http://www.xmlvm.org/clr2jvm, I'm not sure if it's mature enough yet, although it has been around for several years now. XMLvm was made, I believe, primarily for translating Android Java apps to the iPhone, however, its XML-code-translation-based framework is flexible enough to do other combinations (see the diagrams on the site).
As for a reason to do this conversion, maybe there is a need to 'hijack' some of the highly abundant oss code out there and use it within his/their own [Java] project.
Cheers
Rich
Try to look at Net2Java It seems to me the best option for automatic (or semi-automatic at least) conversion from C# to Java
They don't convert directly, but it allows for interoperability between .NET and J2EE.
http://www.mainsoft.com/products/index.aspx
C# has a few more features than Java. Take delegates for example: Many very simple C# applications use delegates, while the Java folks figures that the observer pattern was sufficient. So, in order for a tool to convert a C# application which uses delegates it would have to translate the structure from using delegates to an implementation of the observer pattern.
Another problem is the fact that C# methods are not virtual by default while Java methods are. Additionally, Java doesn't have a way to make methods non virtual. This creates another problem: an application in C# could leverage non virtual method behavior through polymorphism in a way the does not translate directly to Java.
If you look around you will probably find that there are lots of tools to convert Java to C# since it is a simpler language (please don't flame me I didn't say worse I said simpler); however, you will find very few if any decent tools that convert C# to Java.
I would recommend changing your approach to converting from Java to C# as it will create fewer headaches in the long run. Db4Objects recently released their internal tool which they use to convert Db4o into C# to the public. It is called Sharpen. If you register with their site you can view this link with instructions on how to use Sharpen:
http://developer.db4o.com/Resources/view.aspx/Reference/Sharpen/How_To_Setup_Sharpen
(I've been registered with them for a while and they're good about not spamming)
I'm not sure what you are trying to do by wishing to convert C# to java, but if it is .net interoperability that you need, you might want to check out Mono
This is off the cuff, but isn't that what Grasshopper was for?
Well the syntax is almost the same but they rely on different frameworks so the only way to convert is by getting someone who knows both languages and convert the code :) the answer to your question is no there is no "effective" tool to convert c# to java
Possibly you could use jni4net - opensource bridge instead ?
Or list of other options I know.
Why not write it in Haxe (http://haxe.org/) and convert it to whatever you want it to be?