Scanner input = new Scanner(System.in);
    String answer;
    String[] items;
    int categoryNumber = 7;
    int categoryLines = 4;
    File inventory = new File("inventory.txt");
    File monitors = new File("monitors.txt");
    File motherboards = new File("motherboards.txt");
    File cpus = new File("cpus.txt");
    File keyboards = new File("keyboards.txt");
    File harddrives = new File("harddrives.txt");
    File mice = new File("mice.txt");
    File cases = new File("cases.txt");
    File checkout = new File("checkout.txt"); //Checkout file
    File report = new File("report.txt"); //Report file
   
    System.out.println("Choose a section between the following: monitors, motherboards, CPUs, keyboards, HD/SSDs, mice, and cases. Press N to stop browsing.");
    answer = input.next();
       
    while(!answer.equals("N")||!answer.equals("n"))
    {
   
      if(answer.equals("Monitors")||answer.equals("monitors"))
      {
        //Displays the list of monitors
        BufferedReader br = new BufferedReader(new FileReader(monitors));
        String mon = null;
        while((mon = br.readLine()) != null)
        {
          System.out.println(mon);
        }
        System.out.println("\nChoose a section between the following: monitors, motherboards, CPUs, keyboards, HD/SSDs, mice, and cases. Press N to stop browsing.");
        answer = input.next();
      }
      else if(answer.equals("Motherboards")||answer.equals("motherboards"))
      {
        //Displays the list of motherboards
        BufferedReader br = new BufferedReader(new FileReader(motherboards));
        String mb = null;
        while((mb = br.readLine()) != null)
        {
          System.out.println(mb);
        }
        System.out.println("\nChoose a section between the following: monitors, motherboards, CPUs, keyboards, HD/SSDs, mice, and cases. Press N to stop browsing.");
        answer = input.next();
      }
      else if(answer.equals("CPUs")||answer.equals("cpus"))
      {
        //Displays the list of CPUs
        BufferedReader br = new BufferedReader(new FileReader(cpus));
        String cpu = null;
        while((cpu = br.readLine()) != null)
        {
          System.out.println(cpu);
        }
        System.out.println("\nChoose a section between the following: monitors, motherboards, CPUs, keyboards, HD/SSDs, mice, and cases. Press N to stop browsing.");
        answer = input.next();
      }
      else if(answer.equals("Keyboards")||answer.equals("keyboards"))
      {
        //Displays the list of keyboards
        BufferedReader br = new BufferedReader(new FileReader(keyboards));
        String kb = null;
        while((kb = br.readLine()) != null)
        {
          System.out.println(kb);
        }
        System.out.println("\nChoose a section between the following: monitors, motherboards, CPUs, keyboards, HD/SSDs, mice, and cases. Press N to stop browsing.");
        answer = input.next();
      }
      else if(answer.equals("HD/SSDs")||answer.equals("hd/ssds"))
      {
        //Displays the list of hard drives & solid state drives
        BufferedReader br = new BufferedReader(new FileReader(harddrives));
        String hdssd = null;
        while((hdssd = br.readLine()) != null)
        {
          System.out.println(hdssd);
        }
        System.out.println("\nChoose a section between the following: monitors, motherboards, CPUs, keyboards, HD/SSDs, mice, and cases. Press N to stop browsing.");
        answer = input.next();
      }
      else if(answer.equals("Mice")||answer.equals("mice"))
      {
        //Displays the list of mice
        BufferedReader br = new BufferedReader(new FileReader(mice));
        String m = null;
        while((m = br.readLine()) != null)
        {
          System.out.println(m);
        }
        System.out.println("\nChoose a section between the following: monitors, motherboards, CPUs, keyboards, HD/SSDs, mice, and cases. Press N to stop browsing.");
        answer = input.next();
      }
      else if(answer.equals("Cases")||answer.equals("cases"))
      {
        //Displays the list of computer cases
        BufferedReader br = new BufferedReader(new FileReader(cases));
        String c = null;
        while((c = br.readLine()) != null)
        {
          System.out.println(c);
        }
        System.out.println("\nChoose a section between the following: monitors, motherboards, CPUs, keyboards, HD/SSDs, mice, and cases. Press N to stop browsing.");
        answer = input.next();
      }
      else if(answer.equals("N")||answer.equals("n"))
      {
        System.out.println("Enter the number of specific items you would like to buy.");
        int numItem = input.nextInt();
        for(int i = 0; i <= numItem; i++)
        {
          System.out.println("Enter the number of the item you would like to buy.");
          String itemNum = input.next();
         
        }
      }
      else
      {
        System.out.println("Invalid");
        System.out.println("\nChoose a section between the following: monitors, motherboards, CPUs, keyboards, HD/SSDs, mice, and cases. Press N to stop browsing.");
        answer = input.next();
      }
    }

Scanner input2 = new Scanner(inventory);
   
    for(int i = 0; i < 21; i++)
    {
      while(input2.hasNext())
      {
        lines[i] = input2.nextLine();
      }
    }
   
    System.out.println("\nChoose a section between the following: monitors, motherboards, CPUs, keyboards, HD/SSDs, mice, and cases. Press N to stop browsing.");
    answer = input.next();
   
    while(!answer.equals("N")||!answer.equals("n"))
    {   
      if(answer.equals("Monitors")||answer.equals("monitors"))
      {
        //Displays the list of monitors
        for(int i = 1; i < 4; i++)
        {
          System.out.println(lines[i]);
        }
        System.out.println("\nChoose a section between the following: monitors, motherboards, CPUs, keyboards, HD/SSDs, mice, and cases. Press N to stop browsing.");
        answer = input.next();
      }