Implement a java class named HashMapTest and use the main method to experiment by creating an instance of HashMap that can store String keys and Integer values. Try at least the following: a. Add a few key/value pairs to the map. b. Add two different values using the same key. Which value is returned when you use the key? c. Print the size of the map. d. Use a Java for each loop to iterate over the keys in the map and print the values.