1. CS2005
Week 7 Lectures
Set Abstract Data Type

2. Aims Describe the Set Abstract Data Type
CS2005
Aims
Describe the Set Abstract Data Type
Illustrate different implementations of the Set ADT
Describe the Java Iterator concept

3. Learning Outcomes specify the Set ADT
CS2005
Learning Outcomes
specify the Set ADT
write a Java program using one of the java.util set classes
use an iterator
recall the main points of Watt & Brown chapter 9.

4. CS2005
The Set ADT
A set is a collection of elements, without any imposed order

5. Set Concepts Null set (empty set) Universal set Disjoint sets Subset
CS2005
Set Concepts
Null set (empty set)
Universal set
Disjoint sets
Subset
Equality

6. Set ADT Essential Operations create:  Set add: Element  Set  Set
CS2005
Set ADT
Essential Operations
create:  Set
add: Element  Set  Set
contains: Element  Set  Boolean
remove: Element  Set  Set
isEmpty: Set  Boolean

7. Set ADT (ii) Other Operations size: Set  Integer
CS2005
Set ADT (ii)
Other Operations
size: Set  Integer
equals: Set  Set  Boolean
copy: Set  Set
areDisjoint: Set  Set  Boolean
isSubset: Set  Set  Boolean
union: Set  Set  Set
intersection : Set  Set  Set
difference : Set  Set  Set

8. Set Implementations Bitmap e.g. to represent the set { ‘C’, ‘X’ }
CS2005
Set Implementations
Bitmap
e.g. to represent the set { ‘C’, ‘X’ }
see java.util.BitSet class

9. Set Implementations (ii)
CS2005
Set Implementations (ii)
Array
e.g. to represent the set { “baker”, “butcher”, “grocer” }

10. Set Implementations (iii)
CS2005
Set Implementations (iii)
Linked List
Binary Search Tree
Hash Table

11. Sets in Java Collection Classes
CS2005
Sets in Java Collection Classes
HashSet
TreeSet
addAll, retainAll, removeAll operations

12. Iterators need for following concept for sets
CS2005
Iterators
need for following concept for sets
1. for every member, m, of the set s
1.1 process m
Iterator used to solve this problem
public interface Iterator {
public abstract boolean hasNext();
public abstract Object next();
public abstract void remove(); }

13. Using an Iterator java.util.Iterator i;
CS2005
Using an Iterator
java.util.Iterator i;
for (i = s.iterator(); i.hasNext(); ) {
Object obj = i.next();
// the following code processes obj … }

14. CS2005
Sample code
ArraySet
TestArraySet
HTML file