Question

Problem 0 Fix the Collections Practice.java file so that it imports all three classes listed below: HashSet, HashMap, ArrayList Problem 1 - iterating through HashSets Complete the method named sum that accepts a HashSet of type Double as its parameter and returns a double sum - so that adds each element in the HashSet to the total sum and then returns. This method stub has been provided for you. Example: HashSet<Double> containing (5.0, 10.5) would return a sum of 15.5 Example: HashSet<Double> containing {-1.0, 10.5, 3.1) would return a sum of 12.6 Problem 2 - Creating and iterating through ArrayLists Write a method named convert ToArrayList that accepts an int array as its parameter and returns an ArrayList of type Integer containing those same elements in the same order. This method stub is NOT provided for you - method name, parameter(s), and return type must match exactly to receive credit. You should not use the word static Problem 3 - Using ArrayList Methods Complete the method named removeNegatives that accepts an ArrayList of type Integer as its parameter. This method should not have a return statement (void). Your task is to:iterate through the grades ArrayList, removing any negative (0) number in the list. Your method should modify the original grades array - it does not return or print anything to the console. Hint - you can check if your method functioned correctly by printing the values of the ArrayList before and after the method was called and inspecting that all negative numbers were successfully removed. You can also check that the size updated correctly when items were removed. Example: ArrayList<Integer> containing (100, -5,99) would be modified to be size 2, containing (100, 99) in that order. Example: ArrayList<Integer> containing (-3, -5, -100, 0) would be modified to be size 1, containing only (0).

Answer 1

// Implementations of above codes

public class CollectionsPractice
{
   public double sum(HashSet<Double> set)                   // method that adds up all elements in given hashset
   {
       double sum=0.0;
       Iterator<Double> it=set.iterator();
       while(it.hasNext())
       {
           sum+=it.next();
       }
       return sum;
   }
   public void removeNegatives(ArrayList<Integer> grades)   // method that removes all negative elements from given arraylist
   {
       Iterator<Integer> it=grades.iterator();
       while(it.hasNext())
       {
           Integer value=it.next();
           if(value<0)
               it.remove();
       }
   }
}

// Mention in comments of any mistakes or errors are found. Thank you.