1. CSE 1030: Implementing Mixing static and non-static features
Mark Shtern

2. Summary Class this parameter Memory Standard methods compareTo
toString, equals, hashCode
compareTo

3. Ex10 Design and implement a Rectangle class
Attributes
Width
Height
Methods
getArea
Assessors, Mutators
Write application that sorts Rectangles by area

4. Find a Bug
import java.util.*; public class Name { private final String first, last; public Name(String first, String last) { this.first = first; this.last = last; } public boolean equals(Object o) { if (!(o instanceof Name)) return false; Name n = (Name)o; return n.first.equals(first) && n.last.equals(last);
public static void main(String[] args) {
Set<Name> s = new HashSet<Name>();
s.add(new Name("Mickey", "Mouse"));
System.out.println (s.contains(new Name("Mickey", "Mouse"))); }

5. Avoiding code duplication
Constructor Chaining
Delegation to Mutators
Delegation to Accessors

6. Attribute Attribute selection Attribute Caching Money  Cents
Polynomial  Coefficients
Attribute Caching

7. Summary
Objects
Utility Class

8. Utility vs Class State full static this Constructors Methods
State less

9. Utility vs Class Utility Object/Class State less or shared state
static
No public constructors
All static methods
Invocation: ClassName.methodName()
Object/Class
State
Public constructors
Instance variables/ Attributes
Instance
Reference variable/this
Invocation:
objectName.methodName()
Instantiation:
obj Name= new ClassName(...)

10. Standard Methods (Object)
toString()  returns a string that represents the current object
equals()  indicates whether some other object is "equal to" this one
hashCode()  returns an integer (hash code value) for the object. This method is supported for the benefit of containers

11. V Hash Code Examples Object Hash Code Point p1 = new Point(); 112
Object
Hash Code
Point p1 = new Point(); 1
Point p2 = new Point(); V

12. V V Hash Code Examples Object Hash Code Point p1 = new Point(1,2); 112 V
Object
Hash Code
Point p1 = new Point(1,2); 1
Point p2 = new Point(1,1); V

13. Immutable Objects
It is an object whose state cannot be modified after it is created.
String, Double, Integer
No public mutators

14. Features Static Feature Non-static Feature
Mixing Static and Non-Static Feature

15. Incorporating an Invocation Counter
Refractor the Rectangle class to keep track of the number of times the getArea method is used

16. Stamping a Serial Number on Objects
Design a patter that helps to associate unique serial number with every instance of a class
Apply the pattern for Rectangle class. Every rectangle should have a unique serial number that starts at 1 and increments serially.

17. Singleton Pattern
Singleton pattern is restricting the instantiation of a class to one object
Singleton pattern is a design pattern
public static ClassName getInstance();
private static ClassName instance = new ClassName(..);