1    package arrays;
2    //Working with the arrays of primes.
3    public class Primes {
4        public static void main(String[] args) {
5            int[] primes = new int[4];
6            primes[0] = 2;
7            primes[1] = 3;
8            primes[2] = 5;
9            primes[3] = 7;
10           //gives me the highest length of the primes array.
11           System.out.println("length of primes = " + primes.length);
12           //gives me the first variable in the primes array.
13           System.out.println("first prime = " + primes[0]);
14           //gives me the last prime of the primes array using the last known number.
15           System.out.println("last prime = " + primes[3]);
16           //calculates last known number in primes array, using primes array length - 1.
17           System.out.println("last prime = " + primes[primes.length-1]);
18           System.out.println("\nThe initial array ...");
19           int i = 0;
20           while (i < primes.length) {
21               System.out.println(primes[i]);
22               i = i + 1;
23           }
24           //this seems to flip the array. not completely sure how.
25           int temp = primes[0];
26           primes[0] = primes[primes.length-1];
27           primes[primes.length-1] = temp;
28           System.out.println("\nThe final array ...");
29           for (int x = 0; x < primes.length; x = x + 1) {
30               System.out.println(primes[x]);
31           }
32       }
33   }
34