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Key points about native Java Keyword
- The native keyword may be applied to a method to indicate that the method is implemented in a language other than Java.
- The native keyword is used to declare a method which is implemented in platform-dependent code such as C or C++. When a method is marked as native, it cannot have a body and must ends with a semicolon instead.
- The Java Native Interface (JNI) specification governs rules and guidelines for implementing native methods, such as data type conversion between Java and the native application.
native Java Keyword Example
1. Main.java
public class Main {
public native int square(int i);
public static void main(String[] args) {
System.loadLibrary("Main");
System.out.println(new Main().square(2));
}
}
2. Main.c:
#include <jni.h>
#include "Main.h"
JNIEXPORT jint JNICALL Java_Main_square(
JNIEnv *env, jobject obj, jint i) {
return i * i;
}
3. Compile and run:
sudo apt-get install build-essential openjdk-7-jdk
export JAVA_HOME='/usr/lib/jvm/java-7-openjdk-amd64'
javac Main.java
javah -jni Main
gcc -shared -fpic -o libMain.so -I${JAVA_HOME}/include \
-I${JAVA_HOME}/include/linux Main.c
java -Djava.library.path=. Main
4
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