Java语言和C语言混合编程（1）--Java native关键字

可以将native方法比作Java程序同Ｃ程序的接口，其实现步骤为：
1、编写java源程序，add用native修饰

package p2019.p06;

public class NativeAdd {
    public native int add(int a,int b);
}

2、编译java程序，生成NativeAdd.class文件
[root@localhost java]# javac p2019/p06/NativeAdd.java
生成NativeAdd.class NativeAdd.java
3、javah生成.h文件
[root@localhost java]# javah p2019.p06.NativeAdd
生成p2019_p06_NativeAdd.h

    1 /* DO NOT EDIT THIS FILE - it is machine generated */
    2 #include <jni.h>
    3 /* Header for class p2019_p06_NativeAdd */
    4 
    5 #ifndef _Included_p2019_p06_NativeAdd
    6 #define _Included_p2019_p06_NativeAdd
    7 #ifdef __cplusplus
    8 extern "C" {
    9 #endif
 10 /*
 11  * Class:     p2019_p06_NativeAdd
 12  * Method:    add
 13  * Signature: (II)I
 14  */

~~ 15 JNIEXPORT jint JNICALL Java_p2019_p06_NativeAdd_add
16 (JNIEnv *, jobject, jint, jint);~~
17
18 #ifdef __cplusplus
19 }
20 #endif
21 #endif
4、将生成的.h文件拷贝到/usr/java/jdk1.8.0_181-amd64/include/和4、将生成的.h文件拷贝到/usr/java/jdk1.8.0_181-amd64/include/llinux目录下，编译C程序时用
5、编写C程序NativeAdd.c

1 #include <stdio.h>
      2 #include "p2019_p06_NativeAdd.h"
~~      3 JNIEXPORT jint JNICALL Java_p2019_p06_NativeAdd_add(JNIEnv * _env, jobject _obj, jint _a, jint _b)~~
      4 {
      5     return _a+_b;
      6 }