JNI Test

Main.cpp

#include <iostream>
#include "Main.h"

using namespace std;

// /usr/lib/jvm/java-8-oracle/include/linux

JNIEXPORT void JNICALL Java_Main_test__(JNIEnv *env, jobject obj) {
    cout << env << endl;
    cout << obj << endl;
    jclass cls = env->GetObjectClass(obj);
    cout << cls << endl;
}

/*
 * Class:     Main
 * Method:    testMain
 * Signature: ()LMain;
 */
JNIEXPORT jobject JNICALL Java_Main_testMain (JNIEnv *env, jobject obj) {
    return 0;
}

/*
 * Class:     Main
 * Method:    test
 * Signature: (I)V
 */
JNIEXPORT void JNICALL Java_Main_test__I(JNIEnv *env, jobject obj, jint num) {
    cout << num << endl;
}

Main.h

#include <jni.h>

#ifndef MAIN_H
#define MAIN_H
extern "C" {
    /*
     * Class:     Main
     * Method:    test
     * Signature: ()V
     */
    JNIEXPORT void JNICALL Java_Main_test__(JNIEnv *, jobject);

    /*
     * Class:     Main
     * Method:    testMain
     * Signature: ()LMain;
     */
    JNIEXPORT jobject JNICALL Java_Main_testMain(JNIEnv *, jobject);

    /*
     * Class:     Main
     * Method:    test
     * Signature: (I)V
     */
    JNIEXPORT void JNICALL Java_Main_test__I(JNIEnv *, jobject, jint);
}
#endif

Main.java

public class Main {
    private int test = 13;

    public native void test();

    public native Main testMain();

    public native void test(int a);

    public static void main(String[] args) {
        System.loadLibrary("main");
        Main main = new Main();
        main.test();
        main.test(5);
        System.out.println(main.testMain());
    }
}