`Calculator.java`
`01 package trail.lifecycle; 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 void stopSession (); 10 11 public ArrayList <Integer> getStarts (); 12 public ArrayList <Integer> getEnds (); 13 public ArrayList <Double> getGrowthrates (); 14 public ArrayList <Double> getSavings (); 15 public ArrayList <Double> getResults (); 16 17 }`