https://github.com/bytedeco/sample-projects

2018
https://www.youtube.com/watch?v=yzFWaQaLRkM
    MyExample.java/cpp
https://www.youtube.com/watch?v=LZrrqZLhtmw
https://github.com/oltzen/JavaCppExample
https://github.com/oltzen/JavaCppExample/blob/master/src/main/java/de/oltzen/javacppexample/Abc.java



https://github.com/bytedeco/javacpp#accessing-native-apis
// NativeLibrary.h
#include <string>
namespace NativeLibrary {
class NativeClass {
public:
    const std::string& get_property() { return property; }
    void set_property(const std::string& property) { this->property = property + "aaa"; }
    std::string property;
};
}

// NativeLibrary.java
import org.bytedeco.javacpp.*;
import org.bytedeco.javacpp.annotation.*;

@Platform(include="NativeLibrary.h")
@Namespace("NativeLibrary")
public class NativeLibrary {
    public static class NativeClass extends Pointer {
        static { Loader.load(); }
        public NativeClass() { allocate(); }
        private native void allocate();

        // to call the getter and setter functions 
        public native @StdString String get_property(); public native void set_property(String property);

        // to access the member variable directly
        public native @StdString String property();     public native void property(String property);
    }

    public static void main(String[] args) {
        // Pointer objects allocated in Java get deallocated once they become unreachable,
        // but C++ destructors can still be called in a timely fashion with Pointer.deallocate()
        NativeClass l = new NativeClass();
        l.set_property("Hello World!");
        System.out.println(l.property());
    }
}

$ javac -cp javacpp.jar NativeLibrary.java 
$ java -jar javacpp.jar NativeLibrary -nodelete

Generating /data/wrk/prj/cpp/javacpp/nativelib/jnijavacpp.cpp               
Generating /data/wrk/prj/cpp/javacpp/nativelib/jniNativeLibrary.cpp
Compiling /data/wrk/prj/cpp/javacpp/nativelib/linux-x86_64/libjniNativeLibrary.so
g++ -I/home/iharh/.sdkman/candidates/java/8.0.172-zulu/include -I/home/iharh/.sdkman/candidates/java/8.0.172-zulu/include/linux /data/wrk/prj/cpp/javacpp/nativelib/jniNativeLibrary.cpp /data/wrk/prj/cpp/javacpp/nativelib/jnijavacpp.cpp -march=x86-64 -m64 -O3 -s -Wl,-rpath,$ORIGIN/ -Wl,-z,noexecstack -Wl,-Bsymbolic -Wall -fPIC -shared -o libjniNativeLibrary.so 
Keeping /data/wrk/prj/cpp/javacpp/nativelib/jniNativeLibrary.cpp
Keeping /data/wrk/prj/cpp/javacpp/nativelib/jnijavacpp.cpp

generates
linux-x86_64/libjniNativeLibrary.so

$ java -cp ~/Downloads/javacpp-1.4.2.jar:. NativeLibrary
Hello World!aaa



https://github.com/bytedeco/javacpp/blob/master/src/test/java/org/bytedeco/javacpp/AdapterTest.java
https://github.com/bytedeco/javacpp/blob/master/src/test/resources/org/bytedeco/javacpp/AdapterTest.h