Aim

Understand java generic type and bag ADT.

Resources

All Java files you need are found on Learning Mall.

Tips

Check lecture notes for lecture 4 to understand Bag collection before starting.

Bag Implementation – convert IntArrayBag to ArrayBag

At this Lab session, we are going to covert the IntArrayBag class to an ArrayBag class.

Download IntArrayBag.java file from Learning Mall. An IntArrayBag is a collection of int numbers. The same number may appear multiple times in a bag.

Download ArrayBag.java file from Learning Mall. An ArrayBag is a generic collection of                 references to objects (objects has the same type). The same object may appear multiple times in a bag.

Have a look of the declaration of this class.

Task 1: We talked about the two constructors in IntArrayBag class. In ArrayBag class, we will create  two constructors as well. Please use the same idea in IntArrayBag class, to finish the implementation of the second constructor in ArrayBag.

Task 2: Implement a grab() method in ArrayBag class, which takes no parameter, returns a random element from the bag.

Note: make sure you check the condition that the bag is not empty.

Task 3: Have a read of remove() method in IntArrayBag. Implement the same method in ArrayBag.

Note:  the element can be null. Check the countOccurrences() method, use the same idea to deal with null in remove() method.