Implementation of Java Native Interface

Implementation of Java Native Interface

A) Develop a JNI application for giving a string equivalent of a number (integer) entered by the client.
B) Develop a JNI application for displaying factorial of an integer number.
C) Develop a JNI application for checking string palindrome.

(A) Develop a JNI application for giving a string equivalent of a number (integer) entered by the client.

Code:

NumString.java

import java.io.*;
class NumString
{
    public native void str(int num);
    static
    {
        System.loadLibrary("numstring");
    }
    public static void main(String args[])
    {
        try
        {
            BufferedReader br=new BufferedReader(new  
                             InputStreamReader(System.in));
            int num=0;
            System.out.println("Enter number between 1 to 10 to find string
                           equivalent: ");   
            num=Integer.parseInt(br.readLine());
            new NumString().str(num);
        }
        catch(Exception e)
        {
            System.out.println("in main "+e);
        }
    }
}//class

NumImpl.c

#include <stdio.h>
#include "jni.h"
#include "NumString.h"

JNIEXPORT void JNICALL Java_NumString_str
(JNIEnv *env, jobject obj, jint num)
{
    switch(num)
    {
        case 1:printf("One");break;
        case 2:printf("Two");break;
        case 3:printf("Three");break;
        case 4:printf("Four");break;
        case 5:printf("Five");break;
        case 6:printf("Six");break;
        case 7:printf("Seven");break;
        case 8:printf("Eight");break;
        case 9:printf("Nine");break;
        case 10:printf("Ten");break;
    }
}

Output:

  
(B) Develop a JNI application for displaying factorial of an integer number

Code:

Factorial.c

#include <jni.h>
#include <stdio.h>
#include "Factorial.h"
JNIEXPORT void JNICALL Java_Factorial_fact
  (JNIEnv *env, jobject obj, jint num)
{

int i,sum=1;
if(num==0)
{
printf("Factorial is 1");
}
else{
while(num>0)
{
sum=sum*num;
num--;
}
printf("Factorial is %d",sum);
}
}

Factorial.h

#include <jni.h>
JNIEXPORT void JNICALL Java_Factorial_fact (JNIEnv *, jobject, jint);

Factorial.java

import java.io.*;
public class Factorial
{
public native void fact(int a);
static
{
System.loadLibrary("Factorial");
}
public static void main(String[] args)
{
    try
    {
    System.out.println("Enter number: ");
int a=Integer.parseInt(new BufferedReader(new InputStreamReader(System.in)).readLine());
   
    Factorial  j = new Factorial();
    j.fact(a);
    }
    catch (Exception ee)
    {
        System.out.println(ee.getMessage());
    }
   
 }
}

Output:

  
(C) Develop a JNI application for checking string palindrome.

Code:

Palindrome.c

#include <jni.h>
#include <stdio.h>
#include<string.h>
#include "Palindrome.h"
JNIEXPORT jboolean JNICALL Java_Palindrome_palin
  (JNIEnv *env, jobject obj, jchar ch1, jchar ch2)
  {

        if(ch1==ch2)
      {
            return 1;
      }
      else
      {
          return 0;
      }
   
}

Palindrome.h

#include <jni.h>
JNIEXPORT jboolean JNICALL Java_Palindrome_palin
  (JNIEnv *, jobject, jchar, jchar);

Palindrome.java

import java.io.*;
public class Palindrome
{
public native boolean palin(char ch,char ch1);
static
{
System.loadLibrary("Palindrome");
}
public static void main(String[] args)
{
    try
    {
    System.out.println("Enter text: ");
    String str=new BufferedReader(new InputStreamReader(System.in)).readLine();
   
Palindrome  p = new Palindrome();   
    char c[]=new char[str.length()];   
char z[]=new char[str.length()];

    int i=0;
    for(int x=str.length()-1;x>=0;x--)
        {
            z[i]=str.charAt(x);
            i++;
        }
   
   
    int siz=str.length();
    System.out.println();

    for(i=0;i<siz;i++)
        {
            c[i]=str.charAt(i);
            System.out.println(c[i]+"hi");
        }
            System.out.println();
        for(i=0;i<siz;i++)
        {
            System.out.println(z[i]+"hello");
        }

    boolean blnFlags=false;
    for(i=0;i<siz;i++)
        {
        blnFlags=p.palin(c[i],z[i]);

        if(blnFlags==false)
            {
            System.out.println("String is not palindrome");
            break;
            }
        }
        if(blnFlags==true)
        {
            System.out.println("String is palindrome");
        }
    }
    catch (Exception ee)
    {
        System.out.println(ee.getMessage());
    }
   
 }
}

Output: