This loop to modify a arraylist of numbers based on arraylist of strings isnt working

Question

So, in my program you input employee information and the salary you input depends on what you input for designation. If temporary, yo input how much they make per hour, if permanent you input what they make per year. At the end, you have the option to sort by salary, so if they choose that then I must multiply the temporary's per-hour by a set number (1920) in order to convert it to what they make per year. I tried this but I got the messages " The type of the expression must be an array type but it resolved to java.util.ArrayList" and "The type of the expression must be an array type but it resolved to java.util.ArrayList", I got that second one twice.

public static void main(String[] args)
  {
    Scanner in = new Scanner(System.in);
    String Continue = "y";
int Count = 0;
int SortingChoice;
ArrayList<String> Names       = new ArrayList<String>();
ArrayList<String> Department  = new ArrayList<String>();
ArrayList<String> Designation = new ArrayList<String>();
ArrayList<Float>  Salary      = new ArrayList<Float>();

//******************************************************//

do
{
   System.out.println("Enter Employee Name: ");
   String x = in.next();
   Names.add(x);

   System.out.println("Enter Employee Designation ('temporary or permanent'): ");
   String y = in.next();
   Designation.add(y);

   System.out.println("Enter Employee Department: ");
   String z = in.next();
   Department.add(z);

   System.out.println("Enter Employee Salary: ");
   float i = in.nextFloat();
   Salary.add(i);

   System.out.println("Do you wish to add another employee? ('y'/'n'): ");
   Continue = in.next();

   Count = Count + 1;
}
while(Continue.equals("y"));

//***********************************************************************//

System.out.println("Enter sorting Criterion Number: 1. Name, 2.Department, 3. Salary. ");
SortingChoice = in.nextInt();

if(SortingChoice == 1)
{
  Collections.sort(Names);
     for(int i=0; i<Names.size(); i++)
     {
        System.out.println(Names.get(i));
     }
}

if(SortingChoice == 2)
{
  Collections.sort(Department);
     for(int i=0; i<Department.size(); i++)
     {
        System.out.println(Department.get(i));
     }
}

if(SortingChoice == 3)
{
  for(int k=0; k<Salary.size(); k++)
  {
    if(Designation[k].equals("temporary"))
      {
         Salary[k] = Salary[k]*1920;
      }
  }


  Collections.sort(Salary);
     for(int i=0; i<Salary.size(); i++)
     {
        System.out.println(Salary.get(i));
     }
}
  }

What I am most concered about if the loop under if(SortingChoice==3)