Java call c program

Different operating systems support different ways to build native libraries. On Solaris, the following command builds a shared library called libHello-World.

The -G option instructs the C compiler to generate a shared library instead of a regular Solaris executable file. Because of the limitation of page width in this book, we break the command line into two lines.

You need to type the command in a single line, or place the command in a script file. The -MD option ensures that HelloWorld. Of course, on both Solaris and Win32 you need to put in the include paths that reflect the setup on your own machine. At this point, you have the two components ready to run the program. The class file HelloWorld. Because the HelloWorld class contains its own main method, you can run the program on Solaris or Win32 as follows:.

It is important to set your native library path correctly for your program to run. The native library path is a list of directories that the Java virtual machine searches when loading native libraries.

If you do not have a native library path set up correctly, then you see an error similar to the following:. Make sure that the native library resides in one of the directories in the native library path. Make sure that it includes the name of the directory that contains the libHelloWorld. If the libHelloWorld. In Java 2 SDK 1. The " -D " command-line option sets a Java platform system property. Setting the java. In simple terms, just make sure you load the relevant library which contains the function definition, load the library which follows the JNI specification and wraps the target function from the first library, expose native methods from your Java class and you should be good to go.

I'd recommend against raw JNI since it contains a lot of boilerplate code and you would end up cursing yourself if you start wrapping a big C library. JNI enables programmers to write native methods to handle situations when an application cannot be written entirely in the Java programming language, e. Java Native Access is a community-developed library that provides Java programs easy access to native shared libraries without using the Java Native Interface.

Checkout JNAerator. If you are using Windows and MinGW gcc you may need additional flag if you are getting UnsatisfiedLinkError for specific method in lib:. Jonas gave a very elaborated answer, but I think its also really worth checking this website and you will get all your essential answers there :.

I got a solution for this problem. Along with it we need to save the path of created dll file in "Path" under "Environment variable". First make ensure to load your native library or. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Call c function from Java Ask Question.

Asked 10 years, 8 months ago. Active 8 months ago. Viewed 99k times. How to call c function from Java. Seems c is compiler based. Any reference? Improve this question. Ali Irawan Ali Irawan 2, 2 2 gold badges 17 17 silver badges 23 23 bronze badges. Anjana Ravindran. Optional 'thank-you' note:.

Is it possible to call java program from C? Peter Chase. You can do that, but it isn't really "calling" Java code. When you do system in C, you are executing the Java code as a separate process.

If you really want to call Java code from C, within a single process, you can do it. Betty Rubble? Well, I would go with Betty Here are the downsides:. However, if you wish to proceed, read on. We'll then extend this example to show how to support the observer pattern.

To do that, we'll need to do a little more work. We'll assume that this class already exists and that we're not allowed to change it. This class implements a simple list of numbers, with methods to add a number to the list, query the size of the list, and get an element from the list. This is pictured in the following object modeling technique OMT diagram:. This is easy enough, if slightly non-portable: If we're on a platform with bit pointers, we can simply store this pointer in an int; if we're on a platform that uses bit pointers or we think we might be in the near future , we can store it in a long.

The actual code for NumberListProxy is straightforward, if somewhat messy. The static section is run when the class is loaded. Under Solaris, it will expect to find the shared library "libNumberList. Shared library naming conventions may differ in other operating systems.

Most of the methods in this class are declared as "native. I chose to implement these functions in a file called NumberListProxyImpl. It begins with some typical include directives:. The implementation of our native method looks like this:.

Now on to the interesting methods. For more information on this, the types of arguments sent to the function, the unhand macro, and other details of Java's support for native C functions, please refer to the Java Tutorial.

While this "glue" is somewhat tedious to write, it's fairly straightforward and works well. As you can see, we're dealing with an observable number list.

In other words, NumberListProxy needs to be a subclass of java.