1    package arraylistplay;
2    
3    import java.util.ArrayList;
4    
5    //This is similar to the Primes program but seems to use an ArrayList.
6    public class Primes2 {
7        public static void main(String[] args) {
8            //Creating the ArrayList.
9            ArrayList<Integer> primes = new ArrayList<>();
10           primes.add(2);
11           primes.add(3);
12           primes.add(5);
13           primes.add(7);
14           //Outputting info from the ArrayList.
15           System.out.println("size of primes list = " + primes.size());
16           System.out.println("first prime = " + primes.get(0));
17           System.out.println("last prime = " + primes.get(3));
18           System.out.println("last prime = " + primes.get(primes.size()-1));
19           //Establishing a for loop.
20           System.out.println("\nThe initial list = " + primes.size());
21           for (Integer prime : primes) {//I'm curious what this command does, and why it does it.
22               System.out.println(prime); //seems to output primes list
23           }
24           //I'll detail each
25           int temp = primes.get(0); //setting temp to primes.get(o) which is 2
26           primes.set(0, primes.get(primes.size()-1)); //this looks like it will get 0 - end
27           primes.set(primes.size()-1,temp); //this looks like it starts at end and ends with 0 (beginning)
28           //I'll probably detail the same way.
29           System.out.println("\nThe final list ...");
30           //another for statement here...
31           for (Integer prime : primes) { //seems to output the primes information
32               System.out.println(prime); //still don't completely understand primes : primes
33           }//this one seems to use the earlier information which altered the primes list to go backwards.
34   
35       }
36   }
37