`Calculator.java`
`01 package trail.interceptor; 02 03 import java.util.ArrayList; 04 05 public interface Calculator { 06 07 public double calculate (int start, int end, double growthrate, double saving); 08 09 public ArrayList <Integer> getStarts (); 10 public ArrayList <Integer> getEnds (); 11 public ArrayList <Double> getGrowthrates (); 12 public ArrayList <Double> getSavings (); 13 public ArrayList <Double> getResults (); 14 15 public String getTrace (); 16 public void setTrace (String s); 17 18 }`