Develop Reference

Using SymPy (or another CAS) with Java

I am currently developing a project in JavaFX that accepts a mathematical expression and evaluates it. I have managed to get basic operations and a good deal of algebra to work. I have also managed to perform definite integrations using the trapezoid rule.
The main problem I am facing is with indefinite integration. I looked up many symbolic computation libraries online like JCalculus, JavaCalculus, JScience, SymJa and others. But none of them were as good as SymPy in terms of functionality. I wanted to know if there is a way to send commands to SymPy from Java and receive the result back into Java.
I am thinking of providing an installer for my JavaFX app that will install Python and SymPy if necessitated by the solution. I also tried to understand Jython, believing that it would somehow by related to the problem but I could not understand its purpose and its usage.
Please help me. I am quite good at Java and JavaFX but my knowledge of Python is severely low and restricted. Step by step instructions and sample code is extremely appreciated.
Thanks in advance.

If you somehow manage to write sympy equivalent python code from your java input in a file, you can get the output of that code very easily.
Process p = Runtime.getRuntime().exec("python yourfile.py");
Take a look at this.

Convert compiled VB program to Java to use in Android app.

I have several VB programs that I wrote a few years ago in school. Is there any way possible to convert those programs to Java? Or would that it be easier to just rewrite it from scratch? My goal is to create an Android app that combines at least two of the programs into one functional app. This is purely a nonprofit endeavor; I'm a full time firefighter and am looking to put a free tool in the hands of my guys and other firemen who might want to use it.
I've been unable to locate the source code for the programs and have searched for an answer but haven't been able to find a definitive answer as most answers cover the source, not the compiled result. I've downloaded a couple supposed VB decompilers to see the results, but, in order to see the 'full' results, all the ones I've used require purchasing a 'pro' version. I have no problem paying for such a version, but I'd like to know if it's going to work properly before I do.

It would definitely be faster to rewrite them than it would be to devise a way of converting a VB program into Java code. Not only are the languages quite dissimilar, but VB's UI model is nothing like Android's, so it would likely be impossible (or at least impractical) to translate the UI code automatically.

Text to speech converter

I am going to create a Text to speech converter, which can be executed in both Windows, and Linux based systems. Can someone please help me answer the following questions;
What language should i use; Java, C++ or any other?
The program i am going to create should be able to read large chunks of data.
There should be good sound quality.
What are the libraries available to achieve this?
Please share your experiences as well.

Use the language you're most comfortable with. I learned the hard way when I tried to re-code my raytracer in C++, coming from a Python background. It took me weeks to get it to function...
Basically, you'll get frustrated by the nuances of a new language before you can get to coding something, so I suggest you stick with what you know.
That's independent of the language. Just makes sure to read the data in chunks (like 2048 kilobytes at a time). Reading a big file to RAM is not a great idea, as you can't be sure your end user has enough RAM (audio files can get BIG).
This is trivial. I can't help you program good sound quality. That's up to you.
There exist a few implementations of TTS for Linux, so that's all I can recommend. Look at Festival, as it is one of the ones you can actually understand.

Long time ago i had that same idea. I think it is not too complicated and can be done. This is how i would do it:
1- I would use Java, because it is platform independent.
2- If you are going to create an standalone application, it will be the local computer that will do the processing an not an application server, as in the case of web apps. Also i suppose that your program, will be used only by one user at a time. I think you will not have big issues with the amount data to process, if u implement some buffering mechanism.
3- The quality of the sound will depend in various factors such as: noise when recording,format, speed of the sound... Notice that many text to speech applications that exist on the web, the sound quality is ok, but you will never get the feeling that it is a real person, who is reading. (I recommend you a female voice, it sounds better).
4- Regarding to the libraries and another gadgets, this is what i think you might need:
-Java Standard Development Kit(To be able to work with java)
-A good IDE: There a many out there you can get for free. My favourite is eclipse but if you are a beginer with java, you might like to start with netbeans many people say it is more intuitive for learning.
-JLayer Mp3 library This will help you play the sounds in java.
-javax.swing Is a java library that is included in the development kit and allows you to create rich graphical user interfaces. Also if you are new to swing, i would recommend you a great swing IDE, called JFormDesigner, have a look at it, im sure it will speed your development alot(It is a great tool).
I hope my answers can give you some tips.
Update
I think it would be correct to mention also, that the only minimum requirement the users of your app will have in order to run the app is:
JRE(Java runtime enviroment)

This project of text to speech can be made using computer generated voice
so no problem of storing a database for each word and its pronunciation.
Just use the language in which u feel master to urself and apply the concept.....

I do not know anything about text to speech except that it's not easy. That being said, I suggest you stick with the language you are most familiar with. I'm sure Java and C can do it.

Good start for .Net and c++ to Java transition?

I know the .Net framework very well and know where to find things ie: StreamReader, StreamWriter, Graphics, etc, and I know Java has similar things. The syntax is different but quite similar to c++ which I have a lot of native c++ experience. Therefore, what would you recomend as a good starting point for tutorials and such. Thanks

In my new job, I quickly found myself working on a common library in C++, C# and Java. I had no Java knowledge and yet found it pretty intuitive to make simple mods to the Java code - the general C# principle that there is a framework class/namespace for most things you want to do, appear to hold in Java.
The thing that bothers me is that this MO would not teach me tricks and improvements in Java that are specific to that language. That's where I would like to see other answers to this question lead.
In the meantime: http://en.wikipedia.org/wiki/Comparison_of_C_Sharp_and_Java
btw while I found C# and Java pretty congruent, I would not say the same about C++ vs Java.

If you work in eclipse/netbeans/intelliJ it may actually be a no-brainer. Guess at a class name, start typing it and hit ctrl-space (for eclipse, others vary). Regardless of which package it is in, it will find all the classes that match and list them for you faster than you could look them up anywhere else.
The other really nice thing to have on hand is the javadocs for the SDK you are working with--you can code effectively with nothing else. They are online (just search for JDK 6.0 or whatever version) or they can be downloaded from the same place you get the JDK.

The javadocs are your friend - once you figure out some of the main packages in java.*, it's easier to know where to look for specific classes / functionality.
Once you're writing some code, buy Effective Java - it's full of tips for the language, and is just a good programming book.

What's the best/easiest way to manipulate ActiveX objects in Java?

I want to open and manipulate Excel files with ActiveX. I've had success with Python's Win32 Extensions and Groovy's Scriptom libraries on other projects but need to do this is pure Java this time if possible.
I've tried the Jacob Java COM Bridge but that doesn't seem as straightforward or simple to use, and I couldn't get it to retrieve cell values (even though this is the library underlying Scriptom). Are there alternatives?

Jacob is really the tool for the job here. I recommend that you take the time to learn a bit about how COM and ActiveX work, and I think you'll find that it's easier to use. COM is quite an accomplishment, but it's hard. Wrappers like VB make it seem easy (For the limited use that they work for), but it is not at all easy. I have a great book on learning COM, but don't have the name handy right now...
You want to learn about the IDispatch interface (this is what most of Excel's COM interface is developed around). It's a nasty, nasty interface (one of those viral things that you can do so much with it that it becomes impossible to tell what is actually happening) - but learning it is key.
If you are having issues in just one area (i.e. getting a value from a cell), you could grab the source for Scriptom and see what they do (open source, after all!).
Another suggestion is to try to implement some test cases of your code in VBA and make sure that you are correctly thinking through all the return values. When we were doing Excel automation in one of our Java apps, we implemented the general algorithm from Word's VBA, worked through the problem cases, etc... After that, transferring over to Jacob was pretty straightforward.
K

how about http://www.nevaobject.com/_docs/_java2com/java2com.htm -- this is commercial but works better.

Have you looked at JExcelAPI? Instead of using ActiveX this is a Java library which directly reads and writes Excel files.
Not an exact answer to your questions but it might solve the problem just as well, especially if you're looking for a pure Java solution.

There's also JIntegra, which does a similar thing. Also commercial.
And there's JNIWrapper, which does a similar thing. again, also commercial.