Adding To and Removing From an Integer List
File IntegerList.java contains a Java class representing a list of integers. The following public methods are provided:
• IntegerList(int size) -- creates a new list of size elements. Elements are initialized to 0.
• void randomize() -- fills the list with random integers between 1 and 100, inclusive.
• void print() -- prints the array elements and indices
• int search(int target) -- looks for value target in the list using a sequential search algorithm. Returns the index where it first appears if it is found, -1 otherwise.
• void selectionSort() -- sorts the lists into ascending order using the selection sort algorithm.
File IntegerListTest.java contains a Java program that provides menu-driven testing for the IntegerList class. Copy both files to your directory, and compile and run IntegerListTest to see how it works. For example, create a list, print it, and use sequential search to look for an element in the list. Does it return the correct index? Now look for an element that is not in the list. Now sort the list and print it to verify that it is in sorted order.
It is often necessary to add items to or remove items from a list. When the list is stored in an array, one way to do this is to create a new array of the appropriate size each time the number of elements changes, and copy the values over from the old array. However, this is rather inefficient. A more common strategy is to choose an initial size for the array and add elements until it is full, then double its size and continue adding elements until it is full, and so on. (It is also possible to decrease the size of the array if it falls under, say, half full, but we won't do that in this exercise.) The CDCollection class in Listing 6.8 of the text uses this strategy -- it keeps track of the current size of the array and the number of elements already stored in it, and method addCD calls increaseSize if the array is full. Study that example.
1. Add this capability to the IntegerList class. You will need to add an increaseSize method plus instance variables to hold the current number of integers in the list and the current size of the array. Since you do not have any way to add elements to the list, you won't need to call increaseSize yet..
2. Add a method void addElement(int newVal) to the IntegerList class that adds an element to the list. At the beginning of addElement, check to see if the array is full. If so, call increaseSize before you do anything else.
Add an option to the menu in IntegerListTest to test your new method.
3. Add a method void removeFirst(int newVal) to the IntegerList class that removes the first occurrence of a value from the list. If the value does not appear in the list, it should do nothing (but it's not an error). Removing an item should not change the size of the array, but note that the array values do need to remain contiguous, so when you remove a value you will have to shift everything after it down to fill up its space. Also remember to decrement the variable that keeps track of the number of elements.
Add an option to the menu in IntegerListTest to test your new method.
4. Add a method removeAll(int newVal) to the IntegerList class that removes all occurrences of a value from the list. If the value does not appear in the list, it should do nothing (but it's not an error).
Add an option to the menu in IntegerListTest to test your new method.
5. Add a method void addInOrder(int newVal) to the IntegerList class that assumes that the list is sorted in increasing order and adds the given element in its correct (sorted) position. So if the list contained the values 10 20 30 40 50 and you added 25, the new list would be 10 20 25 30 40 50. Don't just stick the value on the end and then sort -- sorting is expensive! Instead, look through the list, figure out where the new value should go and put it there, moving everything after it down to make room for it. As for addElement, you may need to increase the size of the array (determine this and do it first if necessary).
Add an option to the menu in IntegerListTest to test your new method.