【JNI】Find 'jni.h' for MacOS

1. download jdk8 and install.

2. check java version:

   sodino:~ sodino$ java -version
   java version "1.8.0_45"
   Java(TM) SE Runtime Environment (build 1.8.0_45-b14)
   Java HotSpot(TM) 64-Bit Server VM (build 25.45-b02, mixed mode)

3. find ‘java’ original path and ‘java_home’:

   sodino:~ sodino$ which java
   /usr/bin/java
   sodino:~ sodino$ ls -n /usr/bin/java
   lrwxr-xr-x  1 0  0  74 Sep 30  2014 /usr/bin/java -> /System/Library/Frameworks/JavaVM.framework/Versions/Current/Commands/java
   sodino:~ sodino$    /System/Library/Frameworks/JavaVM.framework/Versions/Current/Commands/java_home 
   /Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home

4. get ‘include’ folder and jni.h

   now you will find a ‘include’ folder with in ‘/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home’,
   and open it ‘jni.h’ will be found.