Java Bootcamp – Workbooks and Challenges
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# Workbook 4.5

From the Java Bootcamp Resources, launch the Workbook 4.5 folder.

## Area Calculator

In this workbook, you will calculate the area of a square, rectangle, triangle, and circle.

## Task 1: area of a square

• Function name:
/**
* Name: areaSquare  <------
* @param side (double)
* @return the area (double)
*
* Inside the function:
*  1. If side is negative
*        - prints "Impossible"
*        - shuts the app down
*  2. Calculates the area of the square. A = side²
*/

• Parameters:
/**
* Name: areaSquare
* @param side (double)  <--------
* @return the area (double)
*
* Inside the function:
*  1. If side is negative
*        - prints "Impossible"
*        - shuts the app down
*  2. Calculates the area of the square. A = side²
*/

• Return value:
/**
* Name: areaSquare
* @param side (double)
* @return the area (double) <--------
*
* Inside the function:
*  1. If side is negative
*        - prints "Impossible"
*        - shuts the app down
*  2. Calculates the area of the square. A = side²
*/

• Inside the function:
/**
* Name: areaSquare - returns the area of a square.
* @param side (double)
* @return the area (double)
*
* Inside the function: <---------
*  1. If side is negative
*        - prints "Impossible"
*        - shuts the app down
*  2. Calculates the area of the square. A = side²
*/


$Area = side²$

Use a Math function to calculate side to the power of 2.

## Task 2: area of a rectangle

Write a function that calculates the area of a rectangle.

$Area = length * width$

1. Function name.

/**
* Name: areaRectangle    <------
* @param length (double).
* @param width  (double).
* @return the area (double)
*
* Inside the function:
*  1. If the length OR width is negative
*       - print "Error: impossible" and
*       - terminate the program.
*  2. return the area: length * width
*/


2. Parameters.

/**
* Name: areaRectangle
* @param length (double).  <-----
* @param width  (double).  <-----
* @return the area (double)
*
* Inside the function:
*  1. If the length OR width is negative
*       - print "Error: impossible" and
*       - terminate the program.
*  2. return the area: length * width
*/


3. Return value.

/**
* Name: areaRectangle
* @param length (double).
* @param width  (double).
* @return the area (double)   <------
*
* Inside the function:
*  1. If the length OR width is negative
*       - print "Error: impossible" and
*       - terminate the program.
*  2. return the area: length * width
*/


Inside the function:

1. Check if the length OR width is negative. If so, print "Error: impossible" and terminate the java program.

2. Then, calculate the area of the rectangle and return it.

/**
* Name: areaRectangle
* @param length (double).
* @param width  (double).
* @return the area (double)
*
* Inside the function:  <-----
*  1. If the length OR width is negative
*       - print "Error: impossible" and
*       - terminate the program.
*  2. return the area: length * width
*/


## Task 3: area of a triangle

$Area = base * height \div 2$

/**
* Name: areaTriangle
* @param base: (double).
* @param height: (double).
* @return the area (double)
*
* Inside the function:
*  1. If the base OR height is negative
*      - print "Error: impossible"
*      - terminate the program.
*  2. return the area: base * height / 2
*/


## Task 4: area of a circle

$Area = π * radius²$

How do you get PI? You could set a double equal to 3.14159... but, please don't do that. You can get PI from the Math class. I encourage you to look it up.

Then, write a function that calculates the area of a circle.

/**
* Name: areaCircle
* @return area (double)
*
* Inside the function:
*  1. If the radius is negative
*      - print: Impossible
*      - terminates the program
*  2. returns the area: π * radius2
*/


## Task 5: Calculate the areas

Using the appropriate function, calculate the area for:

• a square with a side of 2 cm.

• a rectangle with a length of 1 cm, and a width of 2 cm.

• a triangle with a base of 1 cm, and a height of 2 cm.

• a circle with a radius of 2 cm.

// double square = area of square with a side of 2.
// double rectangle = area of rectangle with length: 1, width: 2.
// double triangle = area of triangle with base: 1, height: 2.
// double circle = area of circle with a radius of 2.

## Task 6: Write a function that prints every area

Instead of cluttering main()with 4 println statements, write a function that prints every area.

/**
* Name: printAreas -- it prints four areas
* @param square (double)
* @param rectangle (double)
* @param triangle (double)
* @param circle (double)
*
* Inside the function:
*  1. print: ("Square area: <square area>")
*  2. print: ("Rectangle area: <rectangle area>")
*  3. print: ("Triangle area: <triangle area>")
*  4. print: ("Circle area: <circle area>")
*
*/


## Task 7: Call theprintAreasfunction.

From main(), call the printAreas function.

Thank you for using the area calculator
This calculator lets you get the area of﻿:

1 -- Square
2 -- Rectangle
3 -- Triangle
4 -- Circle

Square area: 4.0
Rectangle area: 2.0
Triangle area: 1.0
Circle area: 12.56637061﻿44

## Visualizing the Runtime

After you solve this workbook, I still recommend watching the video solution on Udemy.

It will show you how to visualize the runtime using Visual Studio Code.

##### Related Course: The Complete Spring Boot Development Bootcamp – Become a Java Web Developer

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