stabilize record usage in requires, add examples

examples/jvm-interop/javaSource/Demo.java

@@ -1,15 +1,39 @@
 package javaSource;
 
+import java.util.Arrays;
+
 public class Demo {
+
    static {
       System.loadLibrary("interop");
    }
+
    public static native String sayHello(String num);
-   // public static native int[] mularr(int[] arr);
+
+   public static native int[] mulArrByScalar(int[] arr, int scalar);
+
+   public static native long factorial(long n);
+
 
    public static void main(String[] args) {
-      System.out.println(sayHello("Brendan"));
-      // int[] arr = {10, 20, 30, 40};
-      // System.out.println(mularr(arr));
+
+      // string demo
+      System.out.println(sayHello("Brendan") + "\n");
+
+      // array demo
+      int[] arr = {10, 20, 30, 40};
+      int x = 3;
+      System.out.println("Array " + Arrays.toString(arr) +
+                         " multipled by " + x +
+                         " results in " + Arrays.toString(mulArrByScalar(arr, x)) +
+                         "\n");
+
+      // number + panic demo
+      // This can be implemented more peacefully but for sake of demonstration-
+      // this will panic from the roc side if n is negative
+      // and in turn will throw a JVM RuntimeException
+      long n = -1;
+      System.out.println("Factorial of " + n + " is " + factorial(n) + "\n");
+
    }
 }