import java.util.* // An abst ract data type of mutable bags having elements of type E. A bag is a like a set, except that it can contain multiple copies of the same element. public class HashBagcE> implements Bag ( private Map contents // maintain the invariant that non-null values in this map are strictly > 0 HashBag) contents new HashMapcE, Integer> 0 /* DO NOT CHANGE ANYTHING ABOVE THIS LINE!/ // Return the number of copies o) ot item in the bag. public int count (E item) t //Put your code here throw new Unsupportedoperationexception 0: /1 Add one copy of item to the bag public void add (E item) //Put your code here throw new UnsupportedoperationException ) // Remove one copy of item from the bag public void remove (E item) ( //Put your code here throw new UnsupportedoperationException () // Return all the distinct elements in the bag (i.e. all items whose counts are > 0) public IterablecE> items) ( //Put your code here throw new UnsupportedoperationException ); // Add bag b into the receiver /I Note: the count of an element in a. add (b) is its count in a plus its count in 1b public void add (Bag