JNI - "Cannot open include file: 'jni_md.h'"

I suspect that jni.h is trying to #include <jni_md.h>, which is then failing because you haven't added its location to your include path.

Try adding both of these entries to your C compiler's include path:

• C:\Program Files\Java\jdk1.7.0\include
• C:\Program Files\Java\jdk1.7.0\include\win32

The win32 path might not be necessary, depending on how jni.h is set up.

A Simple Java Native Interface (JNI) example in Java

• env：jdk8、macOS 10.15

// Main.javapublic class Main {    public native int intMethod(int i);    static {        System.loadLibrary("Main");    }    public static void main(String[] args) {        System.out.println(new Main().intMethod(2));    }}

// Main.c:#include "Main.h"JNIEXPORT jint JNICALL Java_Main_intMethod(    JNIEnv *env, jobject obj, jint i){    return i * i;}

Compile and run:

javac Main.java -h .gcc -dynamiclib -O3 \    -I/usr/include \    -I$JAVA_HOME/include \    -I$JAVA_HOME/include/darwin \    Main.c -o libMain.dylibjava -cp . -Djava.library.path=$(pwd) Main

Output:

4

Try this,

HelloWorld.c

#include "HelloWorld.h"#include <stdio.h>JNIEXPORT void JNICALL Java_HelloWorld_print(JNIEnv *env, jobject obj){  printf("Hello World!\n");  return;}

Compile it using cl.exe (I'm using VC++ and CL.EXE required following command line switches.)

c:\>cl -c /I"c:\Program Files\java\jdk1.7.0\include" /I"c:\Prog ram Files\java\jdk1.7.0\include\win32" HelloWorld.c

Link .obj module

c:\>link /libpath="c:\Program Files\java\jdk1.7.0\lib" HelloWorld.obj /dll