JNI, The Java Native Interface
Standard programming interface for writing Java native methods and embedding the Java virtual machine into native applications.
Website: http://download.oracle.com/javase/6/docs/technotes/guides/jni/index.html, http://java.sun.com/docs/books/jni/
Platforms supported: Win32, Linux
Headers to include: jni.bi
Header version: from 2006
Example
Three files:

- `mylib.bas` - A DLL writting in FreeBASIC

`
#include "jni.bi"
'' Note: The mangling must be "windows-ms" or the JRE won't find any function
Extern "windows-ms"
Function Java_MyLib_add( env As JNIEnv Ptr, obj As jobject, l As jint, r As jint ) As jint Export
Return l + r
End Function
End Extern
`

- `Mylib.java` - The Java class that represents the interface to the FreeBASIC code and ensures the FreeBASIC DLL is loaded

    (cpp)
    class MyLib {
    	public native int add( int l, int r );
    	static {
    		System.loadLibrary( "mylib" );
    	}
    }

- `Test.java` - The Java main() that uses the Mylib class

    (cpp)
    class Test {
    	public static void main(String[] args) {
    		MyLib lib = new MyLib();
    		System.out.println( "2+2=" + lib.add( 2, 2 ) );
    	}
    }

Steps to test it:

- Compile the FreeBASIC DLL: `fbc mylib.bas -dll`
- Compile the two Java classes: `javac Mylib.java Test.java`
- Run the `Test` class: `java Test`