What are native methods in Java and where should they be used

Question

A native method has the same syntax as an abstract method  but where is it implemented

User · Answer

Native methods allow you to use code from other languages such as C or C   in your java code  You use them when java doesn t provide the functionality that you need  For example  if I were writing a program to calculate some equation and create a line graph of it  I would use java  because it is the language I am best in  However  I am also proficient in C  Say in part of my program I need to calculate a really complex equation  I would use a native method for this  because I know some C   and I know that C   is much faster than java  so if I wrote my method in C   it would be quicker  Also  say I want to interact with another program or device  This would also use a native method  because C   has something called pointers  which would let me do that

User · Answer

Java native code necessities    h w access and control  use of commercial s w and system services h w related   use of legacy s w that hasn t or cannot be ported to Java  Using native code to perform time-critical tasks    hope these points answers your question

User · Answer

I like to know where does we use Native Methods   Ideally  not at all   In reality some functionality is not available in Java and you have to call some C code   The methods are implemented in C code

User · Answer

The method is implemented in  native  code  That is  code that does not run in the JVM  It s typically written in C or C     Native methods are usually used to interface with system calls or libraries written in other programming languages

User · Answer

What are native methods in Java and where should they be used    Once you see a small example  it becomes clear   Main java   public class Main       public native int intMethod int i       public static void main String   args            System loadLibrary  Main            System out println new Main   intMethod 2              Main c    include  lt jni h gt   include  Main h   JNIEXPORT jint JNICALL Java Main intMethod      JNIEnv  env  jobject obj  jint i      return i   i      Compile and run   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   Output   4   Tested on Ubuntu 14 04 with Oracle JDK 1 8 0 45   So it is clear that it allows you to    call a compiled dynamically loaded library  here written in C  with arbitrary assembly code from Java and get results back into Java   This could be used to    write faster code on a critical section with better CPU assembly instructions  not CPU portable  make direct system calls  not OS portable    with the tradeoff of lower portability   It is also possible for you to call Java from C  but you must first create a JVM in C  How to call Java functions from C     Example on GitHub for you to play with

[java] What are native methods in Java and where should they be used?

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