Example 2 - BrainyNumberSpan

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Overview
Instructions
Class Description
Class
Instance Variables
Constructors
Instance Method Definitions (Explained)
Instance Methods
Download Source Code

In this example we're going to make a class named BrainyNumberSpan.

Read through the challenge general rules and tips
Code the class defined on this page
It is suggested (but not required) to add a test class -- always a good idea
Have a ball! (fun)

Class Description

* Hello I'm class BrainyNumberSpan
*
* I represent a span starting at number 'left'
* and ending on number 'right'
*
* For example, if my 'left' = 10
* and my 'right' = 15
*
* Then I span five numbers (10, 11, 12, 13, and 14)
*
* Note that the 'left' boundary is *included* in the span.
* Note that the 'right' boundary is *excluded* in the span.
*
* My purpose is to provide a user friendly methods to
* operate over my span
*
* The ivars left and right are non-negative integers

Add a class named BrainyNumberSpan.

Remember Java is picky and case sensitive. So it must be "BrainyNumberSpan" and not "brainyNumberSpan", and not "brainynumberspan", etc.

Instance Variables

Add two private ivars named left and right, both of type int.

Also see section "Class Description" above

Brainy number has two standard constructors and one static factory constructor.

Standard Constructors:

A no-arg constructor which initializes the ivars to zero
A two-arg constructor receiving parameters aLeft and aRight, both of type int -- they are used to initialize the ivars

Reminder: arg and parameter are used interchangeably.

Static Factory Constructor

BrainyNumberSpan also has one static factory constructor.

It can be coded as shown here (copy-paste) -- you will learn details about these methods in advanced programming.

/** Static Factory Constructor */
public static BrainyNumberSpan fromLeftRight(int aLeft, int aRight) {
	return new BrainyNumberSpan(aLeft, aRight);
}

Instance Method Definitions (Explained)

Each Method Definition provides a definition of an instance methods that to be added (coded) to BrainyNumberSpan.

Instance Method Definition (Explained)

An example method definition is shown here:

countEasilyDivisible

Returns the count of easily divisible numbers within this span of numbers.

The definition of easily divisible can be found in BrainyNumber.

Example:

For span (1, 10), countEasilyDivisible = 8

Notes Pertaining to the Method Definition Above:

The method name is countEasilyDivisible
Below the method name is a description of the method
Return types and method param types can be derived from the method description
If no method params are mentioned, that means there are no method params for the given method
If no return value is specified then the method does not return a value (i.e., the return type is coded as void)
When a method description uses terminology such as "our number", "this number", "the number", etc it is talking about the num in the particular instance of the brainy or smart number
To the right is additional information such as examples of method usage, example test values, etc

Instance Methods

The following lists the methods to code into the BrainyNumberSpan class.

Reminder: the method headers are more important than the code itself. Here are tips for the method headers:

From the method description we will be able to derive the return type and method param types
If no method params are mentioned, that means there are no method params for the given method
If no return value is specified then the method does not return a value (i.e., the return type is coded as void)

This is the standard toString method. Very helpful for debugging and more.

We can code it just like shown here.

We should add toString to all classes we code.

/** Simply return nice string */
@Override
public String toString() {
	return String.format("[%d - %d]", this.getLeft(), this.getRight());
}

Returns the value of the ivar left. This simple method is called a getter because it gets the ivar.

//Example Usage

BrainyNumber span = new BrainyNumberSpan(1, 10);
prn("Left: " + span.getLeft());
//Left: 1

Returns the value of the ivar right. This simple method is called a getter because it gets the ivar.

//Example Usage

BrainyNumber span = new BrainyNumberSpan(1, 10);
prn("Right: " + span.getRight());
//Right: 10

countEasilyDivisible

Returns the count of easily divisible numbers within this span of numbers.

The definition of easily divisible can be found in BrainyNumber.

Example:

For span (1, 10), countEasilyDivisible = 8

countAbcFactorsGreaterThan

Returns the count of numbers within this span of numbers that have abcFactor greater than parameter threshold.

Receives one method parameter, threshold, an int.

The definition of abcFactor can be found in BrainyNumber.

Example:

For span (1, 101), countAbcFactorsGreaterThan(20) = 23

countAbcFactorsLessThan

Returns the count of numbers within this span of numbers that have abcFactor less than parameter threshold.

Receives one method parameter, threshold, an int.

The definition of abcFactor can be found in BrainyNumber.

Example:

For span (1, 101), countAbcFactorsLessThan(5) = 1

Returns the sum of abcFactors within this span of numbers.

The definition of abcFactor can be found in BrainyNumber.

Example:

For span (11, 20), sumAbcFactors() = 208

Download Source Code

Code up BrainyNumberSpan
As needed or for comparison, download this code for reference

Introduction To Objects With Java (Chapter 603 - Loops)

Chapter 603 - Loops Example 2 - BrainyNumberSpan

Contents Overview Concepts While With Objects With Helpers For Examples Challenges

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