步骤

1. native 声明 c/c++ 里方法 , System.loadLibrary()加载之后生成的so/dll

    public class TestJavaCallC {
   
        public native void sayHello();
   
        public static void main(String[] args){
            System.loadLibrary("NativeCode1");
            TestJavaCallC tNative = new TestJavaCallC();
            tNative.sayHello();
        }
    }
   

2. 生成native方法的头文件

    javah -jni  TestJavaCallC 
   

3. 实现cpp

    #include "TestJavaCallC.h"
    #include<iostream>
   
    using namespace std;
   
    JNIEXPORT void JNICALL Java_TestJavaCallC_sayHello(JNIEnv *, jobject)
    {
        cout << "hello word" << endl;
    }
   

4. 生成 so

   g++  -fPIC   -I/usr/lib/jvm/java-8-jdk/include -I/usr/lib/jvm/java-8-jdk/include/linux   -shared -o libNativeCode1.so  estJavaCallC.cpp
   

5. so移到LD_LIBRARY_PATH，或修改LD_LIBRARY_PATH目录

    export LD_LIBRARY_PATH=..
   

6. 运行

    java TestJavaCallC