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Use GAWK as native function in Java (JNI)

I'm trying to build the GAWK library (c language) as a dll file so I could access it directly from my Java code, without needing to execute an external process (as a "native" function).
As it's easy to do the "helloWorld" JNI, it's quite complicated to do it with GAWK source code, especially for one who isn't familiar with C language.
I need help with 2 things:
How to properly build the complication environment
How to recognize
the place in the code where I should write my "doAwk" function (I
got lost in their code)
Or, if you're familiar with a place where I can find an already working version of it - that would be the best :)
Thanks!

How do you call C++ and\or Java functions from Python 2.7?

I am creating a Windows program that so far has a .bat file calling a .pyw file, and I need functions from Java and C++. How can I do this?(I don't mind creating a new batch or python file, and I already have the header file for the C++ section and a .jar file for my java components. (For Java I use Eclipse Java Mars, and it's Java 8u101)) Thanks!!!

This is rather simple for C++: you have to compile a library with the function, import it in Python and... call it! Python has a powerful ctypes module in the standard library to handle this kind of tasks.
Here is an example of loading print() function from hypothetical libc.dll.
from ctypes import *
libc = cdll.LoadLibrary("libc.dll")
>>> print(libc.time(None))
1150640792
Calling Java from Python is covered here: How to call a java function from python/numpy?

You can load C++ function and execute it from Python like BasicWolf explained in his answer. For Java, Jython might be a good approach. But then there's a problem - you will need to be dependent on Jython which is not up to date with the latest versions of Python. You will face compatibility issues with different libraries too.
I would recommend compiling your C++ and Java functions to create individual binaries out of them. Then execute these binaries from within Python, passing the arguments as command line parameters. This way you can keep using CPython. You can interoperate with programs written in any language.

Calling Matlab from Java for heavy algorithms?

Did anyone made a coupling between Java and Matlab and can advise how this can be done best? Is there eg a framework that I should not miss to look at?
I want to write a java program that hands parameters to a matlab function and gets the result (and pictures created in matlab based on iterations) back.
Further these results shall be displayed on a website, so Java EE JSF will be my choice.
How can this coupling be done best?

You could try JAMAL (JAva MAtlab Linking): http://jamal.khadkevich.org/about.html

Yes, the Mathworks have made a coupling between Java and Matlab and can advise how this can be done best. You might start your reading at this page.

matlabcontrol is a Java API which will allow you to call MATLAB from Java. You can either call MATLAB from within MATLAB or from outside MATLAB in which case an instance of MATLAB is launched and connected to. It allows for invoking eval and feval in MATLAB and returning the results to MATLAB. The walkthrough explains with examples how to do this. The walkthrough uses built-in MATLAB functions and commands, but you can use it with your own .m files because using matlabcontrol is just like interacting with MATLAB's Command Window.

Is it possible to run C source code from Java?

Now I have some C source codes, I would like to use it in my java application.
I need to execute the C source code, and get back the result to my java application. Instead of re-write all the C source code to java, how can I reuse the C's source code in my java application?

Take a look at Java Native Interface.
The Java Native Interface (JNI) is a programming framework that
enables Java code running in a Java Virtual Machine (JVM) to call and
to be called by native applications (programs specific to a
hardware and operating system platform) and libraries written in other
languages such as C, C++ and assembly.

There are the following ways.
JNI (see answer of #AurelioDeRosa +1)
JNA
If your C program can run as command line utility why not just to execute it using Runtime.getRuntime().exec() or ProcessBuilder?

Two options:
Make a library accessible via JNI or JNA
Make an executable, and call it with ProcessBuilder or Runtime.exec and capture the output streem if needed

Yes its possible Take a look at
Calling C Code from Java

Convert Java jar file in to cpp

I have a java code and created a jar file.
I need to create an Qt application. Can I use this code in that application?
Please help me how can i use that jar file.
Thanks,
Nagaraju.

You could take a look at the capabilities of GCC/GCJ (see http://gcc.gnu.org/ ). IF it's a good idea is a whole other story, and depends on what you have, and what you're trying to accomplish. It should be doable to link SO's created with GCJ in QT applications, but I seriously wonder if you are not better off using either C++ or Java, but not mixing them

If your Java code takes input from stdin or some file and writes output to stdout or some file, then the easiest way is to fork java to run that jar, and parse the output in your Qt code.
Things other than that, you'll need to be a bit specific. Something like "my Java code does painting the screen".

My advice is to use SWT or Swing.

You can use gcj gcj to compile the java code to library and simply call the functions of the java code from your C code.

Yes, you can use your jar file in your Qt application. I've done exactly this myself.
One way is to use the JNI Invocation API. This is part of the Java Native Interface (JNI), which makes it feasible but not pleasant to access Java APIs from C++.
A much more pleasant approach is to use CodeMesh JunC++ion, which wraps the Java APIs in C++ classes. This is a great product, if you can afford it.
If you have very little Java code, it may be easier to port it to C++.