public class EqualDifference {
public static void main(String[] args){
int firstNumber = 1;
int lastNumber = 100;
int step = 1;
//or get parameters from command line
if(args.length != 0){
firstNumber = Integer.parseInt(args[0]);
lastNumber = Integer.parseInt(args[1]);
step = Integer.parseInt(args[2]);
}
int total = sum(firstNumber,lastNumber,step);
System.out.println("The sum is: " + total);
}
static int sum(int firstNumber,int lastNumber,int step){
int equalDifferenceLength = (lastNumber - firstNumber + 1)/step;
int total = equalDifferenceLength*(lastNumber + firstNumber)/2;
return total;
}