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This lesson walks you through the steps necessary to integrate native code with Java programs.This lesson implements the canonical "Hello World!" program. The "Hello World!" program has two Java classes. The first, called
Main
, implements themain()
method for the overall program. The second, calledHelloWorld
, has one method, a native method, that displays "Hello World!". The implementation for the native method is provided in the C programming language.Step 1: Write the Java Code
Create a Java class namedHelloWorld
that declares a native method. Also, write the main program that creates aHelloWorld
object and calls the native method.Step 2: Compile the Java Code
Usejavac
to compile the Java code that you wrote in Step 1.Step 3: Create the .h File
Usejavah
to create a JNI-style header file (a.h
file) from theHelloWorld
Java class. The header file provides a function definition for the implementation of the native methoddisplayHelloWorld()
defined inHelloWorld
Java class.Step 4: Write the Native Method Implementation
Write the implementation for the native method in a native language source file. The implementation will be a regular function that's integrated with your Java class.Step 5: Create a Shared Library
Use the C compiler to compile the.h
file and the.c
file that you created in Steps 3 and 4 into a shared library. In Windows 95/NT terminology, a shared library is called a dynamically loadable library (DLL).Step 6: Run the Program
And finally, usejava
, the Java interpreter, to run the program.
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