# 14-interfaces-adts - CSE 143 Lecture 14 Interfaces Abstract...

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Unformatted text preview: CSE 143 Lecture 14 Interfaces; Abstract Data Types (ADTs) reading: 9.5, 11.1; 16.4 slides created by Marty Stepp http://www.cs.washington.edu/143/ 2 Linked vs. array lists • We have implemented two collection classes: – ArrayIntList – LinkedIntList – They have similar behavior, implemented in different ways. We should be able to treat them the same way in client code. • But how? 9 17-3 42 value 3 2 1 index front 42 next data-3 next data 17 next data 9 next data 3 Another example: Shapes • Consider the task of writing classes to represent 2D shapes such as Circle , Rectangle , and Triangle . • Certain operations are common to all shapes: – perimeter: distance around the outside of the shape – area: amount of 2D space occupied by the shape – Every shape has these, but each computes them differently. 4 Shape area and perimeter • Circle (as defined by radius r ): area = π r 2 perimeter = 2 π r • Rectangle (as defined by width w and height h ): area = w h perimeter = 2 w + 2 h • Triangle (as defined by side lengths a , b , and c ) area = √( s ( s- a ) ( s- b ) ( s- c )) where s = ½ ( a + b + c ) perimeter = a + b + c r w h a b c 5 Common behavior • Suppose we have 3 classes Circle , Rectangle , Triangle . – Each has the methods perimeter and area . • We'd like our client code to be able to treat different kinds of shapes in the same way: – Write a method that prints any shape's area and perimeter. – Create an array to hold a mixture of the various shape objects. – Write a method that could return a rectangle, a circle, a triangle, or any other kind of shape....
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14-interfaces-adts - CSE 143 Lecture 14 Interfaces Abstract...

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