Description
Suppose we have a list named list. This is an ADT List using linked list to store a
collection of data. To make it simple for this lab, this ADT List consist of only two methods;
(1) addToFirst(T newEntry) to add newEntry into the first position, and (2) getEntry(int
position) to retrieve an entry at position. As explained in class, if we want to access every
entry in the list sequentially from the first position (position 1) to the last position, we need
to use some type of loop and use the method getEntry() as shown below:
for(int i = 1; i <= numberOfData; i++)
{
getEntryArray[i – 1] = list.getEntry(i);
}
Recall that the method getEntry() needs to call the method getNodeAt(int position)
to obtain the reference to the Node associated with the position. Since we have only the
reference to the first node of the link chain, the method getNodeAt() needs to traverse the
link change starting at the first node every time it is called.
As explained in class, we can improve the performance of sequentially accessing all data
using iterator. An iterator allows us to access the next data without traversing the link chain
from the first node. To access all data using iterator, a user can use a loop as shown below:
int index = 0;
while(iterator.hasNext())
{
iteratorArray[index] = iterator.next();
index++;
}
What to Do?
For this lab, you are going to implement an iterator for this simply ADT List implementation
in SListIterator.java. What you need to do are as follows:
1. Implement the method getIterator() which allows a user to obtain the iterator of
this list
CS 0445 — Data Structures Page 1
Lab 9: Iterator
2. Implement the class IteratorForSList which implements the interface Iterator.
For this class, you have to implements methods hasNext() and next(). The method
remove() is given.
Test Class
The test class SListIteratorTester.java is given. This test class will create a list named
list. Add random numbers into this list. Then retrieve all data sequentially and store
them in the integer array named getEntryArray according to its position using the method
getEntry() (see the first code fragment in the introduction section). Then it will use iterator
and access all data sequentially and store them in the integer array named iteratorArray
according to its position using iterator (see the second code fragment in the introduction
section). Then these two array are compared to ensure the correctness of your iterator
implementation. This test class also time both getEntry() and iterator to show how much
performance is improved using iterator.
Due Date and Submission
For the due date, please check the lab in the CourseWeb. Submit your SListIterator.java
to the CourseWeb under this lab by the due date. No late submission will be accepted.
CS 0445 — Data Structures Page 2
