can you explain this java code and how it works and why was hash set and hash maps used: package javaapplication$30$; import java.util.$*$; $/****$ @author $*/$ public class JavaApplication$30\{/***$ @param args the command line arguments $*/$ public static void main$($String$[]$ args$)\{//$ TODO code application logic here Scanner scanner $=$ new Scanner$($System$.$in$)$; System.out.print$("$Enter the number of frames: $")$; int capacity $=$ scanner.nextInt$()$; System.out.print$("$Enter the page string $($comma$-$separated$)$: $")$; scanner.nextLine$()$; $//$ Consume newline String$[]$ pages $=$ scanner.nextLine$().$split$(",")$; int pageFaultsLRU $=$ simulateLRU$($pages$,$ capacity$)$; System.out.println$("$Number of page faults: $"+$ pageFaultsLRU$)$; int pageFaultsFifo $=$ simulateFIFO$($pages$,$ capacity$)$; System.out.println$("$Number of page faults: $"+$ pageFaultsFifo$)$; $\}$ public static int simulateLRU$($String$[]$ pages, int capacity$)\{$ Set frameSet $=$ new LinkedHashSet$<>($capacity$)$; Map pageLastUsed $=$ new HashMap$<>()$; int pageFaults $=0$; for $($String page : pages$)\{$ if $(!$frameSet.contains$($page$))\{$ pageFaults$++$; if $($frameSet$.$size$()==$ capacity$)\{$ String leastRecentlyUsedPage $=$ null; int minLastUsed $=$ Integer.MAX$\_$VALUE; for $($String framePage : frameSet$)\{$ if $($pageLastUsed$.$get$($framePage$)<$ minLastUsed$)\{$ leastRecentlyUsedPage $=$ framePage; minLastUsed $=$ pageLastUsed.get$($framePage$)$; $\}\}$ frameSet.remove$($leastRecentlyUsedPage$)$; pageLastUsed.remove$($leastRecentlyUsedPage$)$; $\}$ frameSet.add$($page$)$; $\}$ pageLastUsed.put$($page$,$ pageFaults$)$; System.out.println$("$Memory State: $"+$ frameSet$)$; $\}$ return pageFaults; $\}$ public static int simulateFIFO$($String$[]$ pages, int capacity$)\{$ Queue frameQueue $=$ new LinkedList$<>()$; Set frameSet $=$ new HashSet$<>()$; int pageFaults $=0$; for $($String page : pages$)\{$ if $(!$frameSet.contains$($page$))\{$ pageFaults$++$; if $($frameQueue$.$size$()==$ capacity$)\{$ String removedPage $=$ frameQueue.poll$()$; frameSet.remove$($removedPage$)$; $\}$ frameQueue.offer$($page$)$; frameSet.add$($page$)$; $\}$ System.out.println$("$Memory State: $"+$ frameQueue$)$; $\}$ return pageFaults; $\}\}$