https://github.com/houarizegai/jniexample

Steps of using Java Native Interface (mix between Java & C/C++ codes)
https://github.com/houarizegai/jniexample

java-c java-cpp java-native java-native-interface javacpp jni

Last synced: 7 months ago
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Steps of using Java Native Interface (mix between Java & C/C++ codes)

• Host: GitHub
• URL: https://github.com/houarizegai/jniexample
• Owner: HouariZegai
• License: mit
• Created: 2020-04-28T14:20:54.000Z (over 5 years ago)
• Default Branch: master
• Last Pushed: 2020-05-01T01:31:37.000Z (over 5 years ago)
• Last Synced: 2025-01-14T08:10:55.277Z (9 months ago)
• Topics: java-c, java-cpp, java-native, java-native-interface, javacpp, jni
• Language: Java
• Homepage:
• Size: 33.2 KB
• Stars: 4
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

          
# JNI Example

Steps of using Java Native Interface (Call C/C++ methods from Java)

[![License MIT](https://img.shields.io/badge/license-MIT-blue.svg)](LICENSE)

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## Tools/Programs we need in this tutorial

* [JDK](https://www.oracle.com/java/technologies/javase/javase-jdk8-downloads.html)

* [CodeBlocks](http://www.codeblocks.org/downloads)

### Step I: Make Java Code for calling C/C++ method

1. Create a Java Project

2. Create a class named **Hello.java**

3. Write the head of method contains **native** keyword that describe the functions/methods in C++ (like [this](src/Hello.java))

4. Compile the Hello.java class using the IDE or by typing this command in the folder that's contain the class:

       javac Hello.java

    **Note:** If **javac** is not recognized, you need to add the JDK path to the "system environment variable"

### Step II: C/C++ Part

1. Generate the C/C++ JNI header by typing this command:

       javah Hello

    And you will see the **Hello.h** file generated (like [this](native/Hello.h))

2. Create new project of type **Dynamic Link Library** on the CodeBlocks IDE

3. Import the Hello.h file

4. Create new file named **Hello.cpp** and make the implementation of the Hello.h method (like [this](native/Hello.cpp))

5. Add the **jni.h** support to C++ compiler:

    1. Right click on the project and click to **Build Options**

    2. Go to **Other compiler options**

    3. Add this two lines:

    

           -I"\include"

           -I"\include\win32"    

        In my case:

    

           -I"C:\Program Files\Java\jdk1.8.0_231\include"

           -I"C:\Program Files\Java\jdk1.8.0_231\include\win32"

6. Build the project

### Step III: Import the lib in Java & Execute the code

1. From C++ project go to the **bin\Debug** folder and copy the generated library (something like *.dll) and paste it in the java project for example under **src/cpplib** folder

2. Now, go to the Hello.java class and import the library using the **System.loadLibrary** method (see this example [here](src/Hello.java))

3. Create Main method, call the native java method & run the App

### Congratuations you called the C++ method from Java using the Java Native Interface :D

## Thank _You_!

If this tutorial helps you, please :star: this repo and share it with others