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
Related
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.
I just saw the open source project on this in github (googlevr) and my question is how is it possible for C++ work with Java? I can understand that Java is for android stuff and C++ is for graphic, memory and tracking but how does two different compiled language work together?
In C and C++ you can create shared libraries. They are handled a bit differently for each platform, but do roughly the same thing.
Windows creates a .dll
Mac creates a .dylib
Linux creates a .so
These represent executable code that can be called by any process. This means that java code, matlab code, python code, etc can call code written in C/C++. Java uses a feature called JNI (Java Native Interface) to do this. JNI is notoriously tricky to setup and manage, so a lot of people use a library like Swig which essentially manages everything you need related to JNI in order to make calling precompiled C++ code from Java easier.
The key here is "precompiled". Someone, at some point, maybe even you, had to take the source code and compile it into a dll, dylib, or so and you have to have that shared library set up where the code that needs to use it (in this case your java app) can see it so that when the java app starts it can load the shared library and make calls into it.
For java one consideration is that java code is inherently cross-platform. C++ code needs to be compiled against each platform. So when you distribute your java app, you need to make sure you have a shared library available that is accessible for whichever platform it is being run on.
I have poker bot written in C++. I want to compete it with another Poker Academy agent. In order to do that there is an API in JAVA namely "meerkat api".
I have no idea how to call my c++ executable from java api, how does one go about communicating with the independent c++ executable from within a java package?
To get started see:
java.lang.Runtime.exec() family
java.lang.ProcessBuilder
Or if you need to integrate with the C++ app on lower lvl meaning not only "run a program and process the results". You can use the JNI or easier variant JNA, but I have to admit it is pain.
After reading/following #hmjd, Well you can use DefaultExecutor from Apache Commons Exec library to execute commands but it internally uses java.lang.Runtime and java.lang.Process.
I would suggest you to use this library over Runtime because Apache Command Execution APIs are more sophisticated, and provide all and more features than Java Runtime. It also handles exit Values.
I'm writing an application which does image processing using matlab and later displays the result using Java's Interface. Due to certain reasons I've to use both Java and Matlab.
How can I use the matlab function in java ?? How to create and access the interface.
matlabcontrol is a Java API which will allow you to call your image processing functions or scripts and return the results to Java. To get started, take a look at the walkthrough.
MATLAB Builder JA is one option to use MATLAB code in Java. This is a non free toolbox for creating a jar file from MATLAB code in order to be imported to Java. Take care of the restrictions concerning jar file creation.
Using Java classes inside MATLAB is much easier, as you can instantiate Java classes in MATLAB code. Undocumented Matlab is one valuable resource for Java integration in MATLAB.
Check Using Sun Java Classes in MATLAB Software for the official information provided by The MathWorks.
A quick google brought up this http://j-integra.intrinsyc.com/support/com/doc/other_examples/Matlab.htm
Alternatively, can you execute your matlab function from the command line? If so you can use
Runtime.getRuntime().exec("your matlab function")
As of R2016b you can use official MATLAB Engine API for Java, which seems to allow same functionality as matlabcontrol.
hi i would like to incorporate assembly language code with java.. guys give me some idea and example programs like hello world because assembly language is new to me..
The "right" solution is JNI or JNA.
But then it depends on your code. If for example you wish to call command line utility compiled to native code (and it does not matter which language was used for coding of this utility) call it by invocation of command line (use either Runtime.exec() or ProcessBuilder. If it is a library use JNI/JNA. If this is not just a library but for instance MS COM component (ActiveX) use one of available java interoperability projects like Jawin, Jintegra, Jinterop etc.