Java Native Interface | Ioane Omerod | Professional Portfolio

In this homework assignment for my ICS 211 class, we were given a function:

f(x) = x^2 for x < 5
f(x) = x^2 - 3x - 10 for 5 <= x < 10
f(x) = x^2 - 7x - 8 for 10 <= x.

We were tasked with getting a user inputted integer and printing out a table of x and f(x) values that would start at x = 0 and increment by 0.5 until the table reached the user inputted integer. The user interface code and code to print the values of x and f(x) as a table were done in Java. While the code to find the f(x) values based on the user inputted integer was done in C. The main point of the project was to use Java Native Interface to compile and execute code written in both Java and C or C++.

Here is a sample of the code’s output and how I compiled and executed the code:

uhx02:/home/i/ioane808/Homework9% make hw9
javac hw9.java
javah hw9
gcc -ansi -pedantic-errors -Wall -I/usr/java/jdk1.8.0_131/include -I/usr/java/jdk1.8.0_131/include/linux -shared hw9.c -fPIC -o libhw9.so
java -Djava.library.path=. hw9
This program will print a table of x
and f(x) for x from 0 to the user
inputted integer with f(x) being
equal to:
x^2 for x < 5
x^2 - 3x - 10 for 5 <= x < 10
x^2 - 7x - 8 for 10 <= x.
Enter number of x: 3
    x        y
    0.00     0.00
    0.50     0.25
    1.00     1.00
    1.50     2.25
    2.00     4.00
    2.50     6.25

The two hardest parts about this assignment were trying to switch between writing Java and C code and getting everything to compile and execute. Trying to debug and switch between Java and C while coding was a challenge as I had never worked on multiple languages at the same time before, but it’s something I found valuable to be able to switch from one language to another. Getting the files to compile together was also the biggest challenge as I was having trouble including a path for the code to run.