To do: October 20

On the white board:

1. What is a similarity between an abstract class and an interface?

2. What is difference between an abstract class and an interface?

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Tomorrow, I will not be in class. Mr. Newland will be administering a CS survey instrument during class. Will count as participation grade.

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Another example of an interface: List

https://docs.oracle.com/javase/8/docs/api/java/util/List.html

List list1 = new List();

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https://repl.it/@alicefisher/listInterface#Main.java

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List interface

List list1 = new List();

error: List is abstract; cannot be instantiated

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List interface

List list2 = new ArrayList();

list2 = new Stack();

list2 = new LinkedList();

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List interface

List list2 = new ArrayList();

list2 = new Stack();

list2 = new LinkedList();

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An ArrayList IS A List.

A Stack IS A List.

A LinkedList IS A List.

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Go over homework

• goformative: Abstract classes
• goformative: Interfaces

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Abstract classes

Abstract classes are declared abstract and an abstract class may include:

• Instance variables (concrete)
• Constructors (concrete)
• Methods - modifiers/accessors (concrete)
• Defined and implemented within the abstract class
• Abstract methods
• Header and purpose defined
• Not implemented

Interface

• Even more abstract
• All elements are abstract, none are concrete
• No instance variables
• No implementations
• Only names of methods and their basic purpose

What is an interface?

An interface is a list of methods that must be implemented.� �An interface may not contain any implemented methods.��Interfaces cannot have constructors!!!�

Interface Comparable <T>

Type Parameters:�T - the type of objects that this object may be compared to

Compares this object with the specified object for order.

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Interface Comparable <T>

int compareTo(T o)

currentObject.compareTo(parameterObject)

• Returns 0 → objects are equal
• Returns int<0 (negative integer) → current object precedes� parameter object
• Returns int>0 (positive integer) → current object comes after� parameter object

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Repl.it Polygon interface

Repl.it lab sort by vowels

Homework:

Replit labs: Polygon interface and sort by vowels