Programming and Problem Solving with Java

CASE STUDY

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nothing about the types of items in the list, let’s make them be integers. We can then

use a random-number generator to create the items in the list.

Responsibility AlgorithmsThe first responsibility, preparing the GUI components, is

very straightforward. We need an input label, an output label, a text field, and a button.

Generating the list requires a little more thought. The CRC card says that this operation

collaborates with the class Random. This Java class supplies a method that generates a

random number. We can call this method to give us an integer, say, between 0 and 999.

Here is how the method works:

Random rand = newRandom();

value = Math.abs(rand.nextInt()) % 1000 ;

The first line initializes the random-number generator. Each time it is called, the

nextIntmethod returns a random number within the range of the intdata type. The

Math.absmethod converts the result to a nonnegative integer, and the % 1000 limits the

values to three digits.Randomis in java.util.

Which list ADT shall we use? Does the list need to be sorted? It must be sorted only

if we decide to use the searches that require a sorted list. Abstraction lets us write the

primary algorithms without having to decide right away. What size shall we make the

list? Let’s set a constant SIZE to be 100. This way it would be easy to change later.

Generate values

forcounter going from 1 to SIZE

Generate random number

Insert number into list

Class Name: Search Superclass: Applet Subclasses:

Responsibilities Collaborations

Prepare GUI components Label, TextField, Button

Generate list values Random

Get an item

Search the list (item) List

return boolean

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