This question already has answers here:
Does Java have support for multiline strings?
(43 answers)
Closed 7 years ago.
I need to work with long strings containing line breaks in Java. Those are for HTML generation, but it is not the most important here.
I'm aware Java is cripple in a way it doesn't have heredocs. But there are other mechanisms I could use:
1) String concatenation (or StringBuilders), not very readable and copy-pasteable.
2) Storing strings in .properties files, either not very readable, but with higher copypasteability.
3) Storing each "heredoc" in seperate .txt file, quite readable and copypasteable, but resulting in a horde of txt files.
4) Template engines, like Velocity or Freemarker - moves design out of Java, requires a lot of map operations, it would be quite good, but the Velocity syntax and loop/if abilities aren't as readable as for example those from Smarty
Each have pros and contras, I'd like to choose 3 but the management prefers 1 because of pure ideological reasons. I'd like to have some standard for working with heredocs in Java, possibly library that makes things easier. I'd be gratefull for any suggestions (with good arguments) how to work with heredocs.
Thanx
I hate to be "that guy", who suggests that you take a completely different approach than what you asked about, but have you looked at Groovy? It's JVM language, can be mixed freely with Java, and in addition to a bunch of other really nice language features, it has heredocs.
Try Rythm template engine, which is built as a high performance Java template engine with Razor like clean syntax.
Links:
Check the full featured demonstration
read a brief introduction to Rythm
download the latest package or
fork it
Updates
Rythm now has a web site: http://rythmengine.org, and a fiddle site: http://fiddle.rythmengine.org
Related
I work with a language similar to JavaScript that is used for point-of-sale device programming. This language really s*cks and I'm trying to build some kind of framework in Java that "converts" Java code into this language.
I did this using some Regex and parsed the Java files directly. Now I found that this may be not the right/better way and I'm searching for alternatives. Are there any tools for helping me doing so?
I thought I should use some advanced reflection utilities like ASM (http://asm.ow2.org/index.html). Performance is not crucial, so that may be the way.
What do you think?
ANTLR is a terrific parser-generator. I'd look into it. It has a Java grammar already available; I'm not sure if it's Java 5, 6, or 7 (I'm guessing it's 5).
Once you have the AST, your problem will be walking the tree and generating the target code. Good luck.
I suggest to parse Java syntax with JavaCC or similar tool, Java grammar description written long time ago. It can be used to write compiler so probably can also be used to write a converter. Regular expressions are not very good at parsing programming languages.
I've never done anything with it myself, but you could take a look at one of the framework listed at altjs.org, specifically under the Java Ports section, and take a look at one of those frameworks and modify them to your specific needs.
There are at least three ways:
a) Interpret the bytecode. There are some existing interpreters in JS, e.g. DoppioVM. They can be very slow.
b) Compile bytecode to JS. I've seen at least one such attempt and the resulting JS was ugly and not very fast. But this approach can have a good performance (well, it may result in using HashMap instead of JS object and so on). The biggest issue is IMHO while/if reconstruction.
EDIT: OK, is possibly is not so slow, but it is ugly and contains garbage like j2js.invokeStatic("j2js.client.Engine", "getEngine()j2js.client.Engine", null);. The one compiler was https://github.com/decatur/j2js-compiler .
c) Compile Java to JS. You can try Google Web Toolkit or http://j2s.sourceforge.net/ .
This question already has answers here:
Does a Java to C++ converter/tool exist? [closed]
(10 answers)
Closed 8 years ago.
Before someone shoots me down, I am aware of the Java to binary compilers and I'm not after one of those.
I also know there will be no perfect tool that converts everything without any problems. I am aware that missing Java libraries are a major problem; however my source doesn't make use of many Java libraries except for stuff like String and prints. I only want to the tool to create the classes that the Java source references. In the case of the String stuff I am happy to fill in the gaps or fix at a later stage. I just want the tool to do the boring bits so I don't have to do the translation manually.
In the case of required classes etc, I will manually fix those at a later stage but would appreciate a pointer to something that at the very least gets enough of the boring stuff done.
Once again I want the source translated and not a compiler to produce a binary. Basically I want to take some Java stuff and convert it to C++ for later use in other projects.
EDIT
ADDITIONAL NOTES
Sorry if I was not clear in my previous parts of this question. I know that Java is very much different from C++. I have some Java code which is mostly filled with processing arrays and bits and has almost no object creation. In a sense it is very self-contained and has few calls to other classes. These classes seem to be prime candidates for conversion; the other stuff will have to be rewritten but at the least some parts are leveraged.
j2c is one - it will convert Java source code into its rough C++ equivalent.
Obviously there are many caveats that others have mentioned (garbage collection, synchronization, etc) but it will provide a good starting point (and it's open source at that so you can easily improve that point =).
Depending on the size of your code base, it might also make sense to roll your own - writing one is not all that hard once you have a Java AST to work with given that the Java syntax is mostly a subset of C++, and there are many libraries which will parse Java code for you (j2c uses the one that comes with Eclipse for example). Doing a conversion by hand is a lot more error-prone than writing a tool for it.
I am asked to develop a software which should be able to create Flow chart/ Control Flow of the input Java source code. So I started researching on it and arrived at following solutions:
To create flow chart/control flow I have to recognize controlling statements and function calls made in the given source code Now I have two ways of recognizing:
Parse the Source code by writing my own grammars (A complex solution I think). I am thinking to use Antlr for this.
Read input source code files as text and search for the specific patterns (May become inefficient)
Am I right here? Or I am missing something very fundamental and simple? Which approach would take less time and do the work efficiently? Any other suggestions in this regard will be welcome too. Any other efficient approach would help because the input source code may span multiple files and can be fairly complex.
I am good in .NET languages but this is my first big project in Java. I have basic knowledge of Compiler Design so writing grammars should not be impossible for me.
Sorry If I am being unclear. Please ask for any clarifications.
I'd go with Antlr and use an existing Java grammar: https://github.com/antlr/grammars-v4
All tools handling Java code usually decide first whether they want to process the language Java or Java byte code files. That is a strategic decision and depends on your use case. I could image both for flow chart generation. When you have decided that question. There are already several frameworks or libraries, which could help you on that. For byte code engineering there are: ASM, JavaAssist, Soot, and BCEL, which seems to be dead. For Java language parsing and analyzing, there are: Polyglot, the eclipse compiler, and javac. All of these include a complete compiler frontend for Java and are open source.
I would try to avoid writing my own parser for Java. I did that once. Java has a rather complex grammar, but which can be found elsewhere. The real work begins with name and type resolution. And you would need both, if you want to generate graphs which cover more than one method body.
Eclipse has a library for parsing the source code and creating Abstract Syntax Tree from it which would let you extract what you want.
See here for a tutorial
http://www.vogella.de/articles/EclipseJDT/article.html
See here for api
http://help.eclipse.org/indigo/topic/org.eclipse.jdt.doc.isv/reference/api/org/eclipse/jdt/core/dom/package-summary.html#package_description
Now I have two ways of recognizing:
You have many more ways than that. JavaCC ships with a Java 1.5 grammar already built. I'm sure other parser generators ditto. There is no reason for you to either have to write your own grammar or construct your own parser.
And specifically 'read[ing] input source code files as text and search for the specific patterns' isn't a viable choice at all, as it isn't parsing, and therefore cannot possibly recognize Java programs correctly.
Your input files are written in Java, and the software should be written in Java, but this is your first project in Java? First of all, I'd suggest learning the language with smaller projects. Also you need to learn how to use graphics in Java (there are various libraries). Then, you should focus on what you want to show on your graphs. Or is text sufficient?
The way I would do it is to analyse compiled code. This would allow you to read jars without source and avoid parsing the code yourself. I would use Objectwebs ASM to read the class files.
Smarter solution is to use Eclipse's java parser. Read more here: http://www.ibm.com/developerworks/opensource/library/os-ast/
Or even more easy: Use reflection. You should be able to compile the sources, load the classes with java classloader and analyse them from there. I think this is far more easy than any parsing.
Our DMS Software Reengineering Toolkit is general purpose program analysis and transformation machinery, with built in capability for parsing, building ASTs, constructing symbol tables, extracting control and data flow, transforming the ASTs, prettyprinting ASTs back to text, etc.
DMS is parameterized by an explicit language definition, and has a large set of preexisting definitions.
DMS's Java Front End already computes control and data flow graphs, so your problem would be reduced to exporting them.
EDIT 7/19/2014: Now handles Java 8.
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Closed 10 years ago.
I've been doing web application development for the last 3 years in PHP. I'm now on the verge to give Java a go. My last use of the language was nearly 8 years ago and was mostly academic.
I'm reasonably well acquainted with PHP's object model (version 5) and I have almost exclusively been coding in OO. I would now like to transport that experience and use it to develop in Java.
Where I'm coming from:
linux as a desktop and server
Vim/gVim + plugins as an editor
MySql for db
apache httpd
experience with a bunch of PHP frameworks, Zend+Doctrine being the ones I use most
What I've garnered so far about a move to Java:
I need an IDE: IntellijIDEA, NetBeans or Eclipse
I need to pick a development framework. Some recurrent names: Spring MVC, stripes, wicket.
Now I need some insight that could help make this transition smoother. But from the way people talk about it, Java seems to be an entirely new beast with its own ecosystem. It sounds as though moving to Ruby or Python would actually be easier, which is curious since, when I look at it, Java conceptually seems the closest to PHP, albeit stricter and precompiled.
As weird as this may sound, very few people have publicly documented their experience of such moves. I have searched google, amazon and stackoverflow for similar questions and the results leave to desire. I just can't believe that I would need to start the same as a newbie if I wanted to be productive as a web developer in Java fast.
Anybody is welcome to respond, but I somewhat think that people with some valuable experience in both languages would enrich this discussion the most.
What helped you get going quickly in Java?
What concepts are omnipresent in Java and absent from PHP and vice versa?
Some gotchas for PHP developers going Java.
How long before you felt the transition was complete?
I wouldn't try to learn an IDE at the same time as learning a language. An easier transition would be to stick to your shell and habitual text editor, and use the following shell-friendly tools:
ant, for organising your project, running automated test suites, incremental compiles
BeanShell for interactive testing, trying things out quickly
A quick trick: javap from the commandline will give method signatures for any class in the standard library. Similar to php -r but gives more information since Java is typed.
The online documentation for Java is precise, professional, and consistent in tone and format. Unlike in PHP where all of the functions are in one flat namespace, the standard libraries in Java are class hierarchies. You've got to know your way around that standard library, which means knowing hierarchies + responsibilities: for example you've got to know that java.util.List is a subinterface of java.util.Collection with the addition of a concept of ordered entries. With that information in your head, a google search for java.util.List will take you to the Javadoc for the class, and the Javadoc will tell you exact method signatures and link you to a selection of concrete implementations.
Some miscellaneous distinctions:
Strings are sequences of characters rather than sequences of bytes. Absolutely the right way of doing it.
Systems produce and consume streams (of bytes or characters) rather than byte buffers. For example, if you wanted to filter the output in PHP, a standard practice is to ask ob_get_contents for a byte buffer then to transform the whole buffer. In Java, you add a filter to your servlet that transforms the output a byte or a character at a time. It's a bit imposing to work with initially but it's simpler and more Lego-like when you get used to it - your stream processor doesn't have to know where things come from and where they go.
Almost everything useful is an interface, and creating an instance of an interface can be tricky, non-standardised, and not always well-documented. In PHP, you can get up and running with XML with new DOMDocument(). In Java, org.w3c.dom.Document is an interface, so new() won't work. Javadoc is very precise about how interface instances behave once they come into existence, but it can be quite coy and prudish when you're trying to find out how an object is actually born. Very often, you'll have to look for tutorials and code examples and copy-paste a piece of boilerplate that gives you an instance of DOMDocument or java.sql.Connection or whatever. One reason frameworks like Spring are popular is that they separate out the ugly object-creation code and present you with a world where interface implementations are just magically there.
I actually switched in the opposite direction. I found that Java works very well in a large company where you might be working on a single component, handing it off to someone else who integrates that component into a larger system, which is then packaged and handed off to a separate operations team - that's where all this indirection and configurability (FactoryBuilderFactory type abstractions, web.xml files, etc) makes sense and does something useful. In a small company where the programmers are the ops personnel, Java is a lot more work. With Java, you'll have to get used to concepts like starting up the Java process, monitoring the Java process to make sure it stays up, monitoring the Java process to make sure that it doesn't go into a coma where it's alive but not responding, shutting down and restarting the Java process with minimal disruption when you're updating code, etc, etc. If you have separate ops personnel, that's fine, it's their job, they're very good at it. If you're a programmer, babysitting a Java process can be distracting and difficult to do well.
Start with the Java Tutorial
http://java.sun.com/docs/books/tutorial/getStarted/index.html
Then go buy Head First Java
http://oreilly.com/catalog/9780596004651
It will get you going pretty quickly in the language which is essential regardless of what you want to do.
Strictly speaking, you don't need an IDE to work in Java. I've been coding heavily in Java for well over a decade (and heavily on other stuff for over 25 years), and I don't much like IDEs. Perhaps that implicit indicator of my age is part of the issue :-) It's a trade-off, like anything else.
I'll plug Stripes as a nice simple framework, but mostly that's because it's relatively small and limited in scope. The large frameworks like Spring are "kitchen sink" ecosystems, and learning Java with one of those frameworks may smooth some of the difficult parts but leave other basic aspects mysterious. Again, it's a matter of personal preference.
It's good to have somebody around who knows the language. Oh, and to that point, make a friend of the Java API documentation. As platforms go, the Java API has its ups and downs but for the most part the documentation is at least pretty thorough and pretty accurate.
You'll also want to get really familiar with JSP and its relationship to Java and Java web service architectures, because that'll be what you'll relate to your PHP experience most directly (I'd think).
The best move I made was from Java to PHP.
Beware of complexity. Primarily, the key to great software is simplicity, and that is why PHP combined with a good framework kills Java.
With Java, you risk becoming a slave to your servlet container and framework. Choose the simplest most flexible framework. Controls and custom tags are the devil. You'll waste days learning things that were designed to make development quicker, but are ultimately too complex and inflexible. Java will slow development due to: complexity, compilation, and static types. You'll come to loathe null pointer exceptions.
Edit: Tools aside, Java and PHP are very similarly structured "C" style languages. Much more so than Python or Ruby. It is the static typing and complex tools that make Java so foreign.
I recommend hitting up JavaBat at here
It will give you some good ideas. It took me 1 solid year in a professional setting to get a very firm grasp on Java and I have been able to move into other OO languages quite easily once I had the thoughts beaten into me.
This appears to be a bit of an old post, but hey...
I moved from C# to Java and I've just started a role and am moving from Java to PHP...
First off: Java is awesome :)
for your IDE get Eclipse, once you get used to it, you never have to leave the IDE (apart from SQL bits). It manages projects really well, you can download alsorts of plugins, such as SVN plugins. It allows you to run a Tomcat server within Eclipse and it will output errors straight to the Eclipse console.
for the framework, I used Struts and Tiles and Torque for the ORM, took me a while to get my head around them, but once we made friends, I can't imagine any other way of developing. Although I imagine for a small project it would be a lot of overhead!
agreed with an above post - get HEADFIRST JAVA, thats how I learnt and I used it for lots of other languages, they have a visual method of learning thats alot easier than pure textbooks - well for me anyway. I was up and running with in a day and confident within a couple of weeks I guess - but always learning :)
yip Java is strict, but you come to love it, for me moving to loose 'ol PHP is a bit wierd.
you will also need to download Tomcat to run your Java bits, its easy as to get running.
Java organises all your classes very nicely, none of this 'require_once(some_text_file.php)' rubbish, just 'import myClass' and off you go.
one of the things that annoys me is, there is no way of telling which JAR libraries you are NOT using, so after a couple of years working on a site, your lib folder can get a bit messy - specially if mulitple people are removing and adding functionality.
I could go on.
Paul
For my case, I only dealt with lot of procedural coding on the php, so jumping to Java, not only did I find everything to be more verbose and less forgiving than php (but now I know why it must be this way, and I love Java a lot) but learning to organizing my code in classes and also learning the eclipse IDE took about 1.5 years of just tinkering, trial & error, making stuff on my own (mainly swing applications).
I guess just creating stuff on your own, utilizing the vast amount of Java libraries out there to build your own stuff is fun is the fastest way. Also I think I could've saved more time by reading the java sun tutorials thoroughly. Even more time saving is making sure you've done a thorough search for libraries that prevent "reinventing the wheel".
Good luck!
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?