import java.util.*;
import java.io.*;

class Assignment5{
public static void main(String[] args)throws Exception{
  String data;

  ArrayList<Double> store = new ArrayList<Double>();
  Scanner scanner = new Scanner(System.in);

  System.out.println(" ");
  System.out.println("Please enter the name of a file with .txt at the end.");
  System.out.println(" ");
  data = scanner.nextLine();

  File inputFile = new File(data);
  Scanner reader = new Scanner(inputFile);

  while(reader.hasNext()){
    store.add(reader.nextDouble());
  }

  calculateSum(store);
  store.clear();

}

private static void calculateSum(ArrayList<Double> ArrayList){
  double sum = 0;
  double avg = 0;
  double total = 0;
  double totalrainfall = 0;

  Iterator<Double> iterator = ArrayList.iterator();

  while(iterator.hasNext()){
    sum += iterator.next();
  }

  total = ArrayList.size();
  avg = (sum / total);

  System.out.println(" ");
  System.out.println("The total rainfall is " + totalrainfall);

}

import java.util.*;
import java.io.*;

class Assignment5{
public static void main(String[] args)throws Exception{
  String data;

  ArrayList<Double> store = new ArrayList<Double>();
  Scanner scanner = new Scanner(System.in);

  System.out.println(" ");
  System.out.println("Please enter the name of a file with .txt at the end.");
  System.out.println(" ");
  data = scanner.nextLine();

  File inputFile = new File(data);
  Scanner reader = new Scanner(inputFile);

  while(reader.hasNext()){
    store.add(reader.nextDouble());
  }

  calculateSum(store);
  store.clear();

}

private static void calculateSum(ArrayList<Double> ArrayList){
  double sum = 0;
  double avg = 0;
  double total = 0;
  double totalrainfall = 0;

  Iterator<Double> iterator = ArrayList.iterator();

  while(iterator.hasNext()){
    sum += iterator.next();
  }

  total = ArrayList.size();
  avg = (sum / total);

  System.out.println(" ");
  System.out.println("The total rainfall is " + totalrainfall);

}

80.0
70.0
75.0
// ...

import java.util.;
import java.io.;

class Assignment5
{

    public static void main(String[] args) throws Exception
    {
        String data;
        int[] store = new int[12];
        Scanner scanner = new Scanner(System.in);

        System.out.println(" ");
        System.out.println("Please enter the name of a file with .txt at the end.");
        System.out.println(" ");
        data = scanner.nextLine();

        File inputFile = new File(data);
        Scanner reader = new Scanner(inputFile);

        while(reader.hasNext())
        {
            String currentLine =  scanner.nextLine();
            String[] currentMonthDetails = currentLine.split(".");
            int currentMonth = Integer.parseInt(currentMonthDetails[0]);
            int currentRainfall =  Integer.parseInt(currentMonthDetails[1]);
            store[currentMonth] = currentRainfall;
        }

        calculateSum(store);
        store = null;
    }

    private static void calculateSum(int[] aRainfallData)
    {
        int avgRainfall = 0;
        int numberOfMonths = 0;
        int totalRainfall = 0;

        numberOfMonths = aRainfallData.length;

        for (int index=0; index < numberOfMonths ; index++)
        {
            totalRainfall += aRainfallData[index];
        }

        avgRainfall = (totalRainfall / numberOfMonths );

        System.out.println(" ");
        System.out.println("The total rainfall is " + totalRainfall );
    }
}

double sum = 0;
boolean toggle = false;
for(Object d: arrayList) {
  [...]
  if(toggle) {
    sum += (Double)d;
    toggle = !toggle;
  }
}