best_i_can_do.java

import java.util.ArrayList;
import java.util.List;
import java.util.Map;

/**
 * Average Expense Calculator
 */
public class Average_Expense_Calculator {

    public Integer average(Map<String, List<Integer>> expenses) { 
      int totalExpenses = expenses.values().stream().flatMap(Collection::stream).mapToInt(Integer::intValue).sum();
      return totalExpenses / expenses.size()
    }
}