The document discusses different sorting algorithms and methods. It introduces the concept of sortable objects that implement the Comparable interface and defines sorting algorithms like insertion sort, shell sort, selection sort, bubble sort, and quicksort. It also describes how sorting is implemented for arrays and collections in Java and the classes and methods involved in the sorting process.

1. Sorting
Chapter 18

2. 18
Creating Sortable Objects
Objects are sortable when they
implement the Comparable interface.
Must implement compareTo() method
Programmer must decide how to compare
objects.

3. 18
Sorting Arrays
TreeSet collections are sorted by
default.
Arrays class includes a sort() method.
Items in array must be sortable
(implement the Comparable interface).

4. 18
Sorting Algorithms
Sortable interface
Provides framework for sort classes
Defines what it means to be sortable
SortList class
Holds the items in the list in an internal
ArrayList
Tracks:
Number of items in the list
Number of comparisons
Number of exchanges
Indicates whether algorithm steps should be displayed

5. 18
The Nested SortItem Class
SortItem class:
Implements Comparable interface
Uses the compareTo() method to
compare current object to an object
passed in
Uses the exchangeValues() method to
exchange values when required

6. 18
Sorting Algorithms
SortDriver class:
Creates a sort object and submits a list to test
the algorithm
Will be modified several times as new sort
algorithm classes are created
SortAlgorithm class:
Abstract base class (used to derive all sort
algorithm classes)
Provides common methods used by all the sort
algorithms

7. 18
Insertion Sort
Recursive insertion:
Compare new object
to each object in the
list until you find
one of lesser value.
Requires a lot of
comparisons and
exchanges.

8. 18
Shell Sort
The shell sort is a variation on the
insertion sort.
Divides list into smaller sublists
Sorts each sublist individually
Then sorts sublists together
Requires many comparisons, but fewer
exchanges

9. 18
Selection Sort
Selection sort:
Scans list to find lowest value then moves
it to the left
Repeat to find next lowest value
Many comparisons with minimal
exchanges

10. 18
Bubble Sort
Bubble sort:
Compares each item to its neighbor and
exchanges if necessary
Largest items “bubble” to the top
Poor performance due to many
comparisons and many exchanges

11. 18
Quicksort
Most widely used sort method
Partitions the list
Use “pivot” to create right and left side
Move item from left to right if larger than pivot
Move item from right to left if smaller than pivot
Each side is then partitioned and algorithm recurses
until list is sorted

12. 18
Comparison of Sort Algorithms
Direct comparison
using random values