Methods

Lab Objectives

Be able to write methods

Be able to call methods

Be able to write javadoc comments

Be able to create HTML documentation using the javadoc utility

Introduction

Methods are commonly used to break a problem down into small manageable pieces. A large task can be broken down into smaller tasks (methods) that contain the details of how to complete that small task. The larger problem is then solved by implementing the smaller tasks (calling the methods) in the correct order.

This also allows for efficiencies, since the method can be called as many times as needed without rewriting the code each time.

Finally, we will use documentation comments for each method, and generate HTML documents similar to the Java APIs that we have seen.

Score	Section
10	Task #1
30	Task #2
30	Task #3
30	Task #4
100	Total Points

Task #1 void Methods

Points	Grading Scheme
2	Does the code compile and run? (No syntax errors)
6	Requested modification correct
2	Is the input/output correct? (Correct data output/Format correctly)
	Paste a copy of your screenshot of your output

Load the file Geometry.java from the CIS260 Ch05 Student Files folder into NetBeans.

This program will compile, but, when you run it, it doesnt appear to do anything except wait. That is because it is waiting for user input, but the user doesnt have the menu to choose from yet. We will need to create this.

Below the main method, but in the Geometry class-under // TASK #1 Create the printMenu method here, create a static method called printMenu that has no parameter list and does not return a value. It will simply print out instructions for the user with a menu of options for the user to choose from. The menu should appear to the user as:

This is a geometry calculator

Choose what you would like to calculate

Find the area of a circle

Find the area of a rectangle

Find the area of a triangle

Find the circumference of a circle

Find the perimeter of a rectangle

Find the perimeter of a triangle

Enter the number of your choice:

Add a line in the main method that calls the printMenu method as indicated by the comments.

Compile, debug, and run. You should be able to choose any option, but you will always get 0 for the answer. We will fix this in the next task.

Take a screenshot of the output and paste it here.

Paste the screenshot of your results here!

Task #2 Value-Returning Methods

Points	Grading Scheme
30	Requested modification correct
	Copy these methods below

Write a static method called circleArea that takes in the radius of the circle and returns the area using the formula A = ? r ².

Write a static method called rectangleArea that takes in the length and width of the rectangle and returns the area using the formula A = lw.

Write a static method called triangleArea that takes in the base and height of the triangle and returns the area using the formula A = bh.

Write a static method called circleCircumference that takes in the radius of the circle and returns the circumference using the formula C = 2?r.

Write a static method called rectanglePerimeter that takes in the length and the width of the rectangle and returns the perimeter of the rectangle using the formula P = 2l +2w.

Write a static method called trianglePerimeter that takes in the lengths of the three sides of the triangle and returns the perimeter of the triangle which is calculated by adding up the three sides.

Paste the copy of your methods here!

Task #3 Calling Methods

Points	Grading Scheme
18	Requested modification correct and Results corrected
12	Hand calculated Values correct
	Fill in the table

Add lines in the main method in the GeometryDemo class which will call these methods. The comments indicate where to place the method calls.

Below, use the sample data (Input Values) and hand calculated the results to test all 6 menu items.

Compile, debug, and run. Test out the program using your sample data. Paste the results here.

Function Name	Input Values	Hand Calculated Results	Program Results
circleArea	radius = 5
rectangleArea	length = 4 width = 6.5
triangleArea	height = 4 base = 3
circleCircumference	radius = 5
rectanglePerimeter	length = 4 width = 6.5
trianglePerimeter	side1 = 3 side2 = 4 side3 = 5

Task #4 Java Documentation

Points	Grading Scheme
30	Requested Documentation is correct
	Compress Project folder and submit for grading

Write javadoc comments for each of the 7 static methods you just wrote. They should include:

A one line summary of what the method does.

A description of what the program requires to operate and what the result of that operation is.

@param listing and describing each of the parameters in the parameter list (if any).

@return describing the information that is returned to the calling statement (if any).

For example:

/**

* Function circleArea -- calculates the area of a circle

* area = PI * r * r

* @param r holds the value of the radius of the circle

* @return the (double) area of the circle

*/

Paste a copy of your source code here.

Source Code

import java.util.Scanner;

/** This program demonstrates static methods */

public class Geometry { public static void main(String[] args) { int choice; // The user's choice double value = 0; // The method's return value char letter; // The user's Y or N decision double radius; // The radius of the circle double length; // The length of the rectangle double width; // The width of the rectangle double height; // The height of the triangle double base; // The base of the triangle double side1; // The first side of the triangle double side2; // The second side of the triangle double side3; // The third side of the triangle

// Create a scanner object to read from the keyboard Scanner keyboard = new Scanner(System.in);

// The do loop allows the menu to be displayed first do { // TASK #1 Call the printMenu method

choice = keyboard.nextInt();

switch(choice) { case 1: System.out.print("Enter the radius of " + "the circle: "); radius = keyboard.nextDouble();

// TASK #3 Call the circleArea method and // store the result in the value variable

System.out.println("The area of the " + "circle is " + value); break; case 2: System.out.print("Enter the length of " + "the rectangle: "); length = keyboard.nextDouble(); System.out.print("Enter the width of " + "the rectangle: "); width = keyboard.nextDouble();

// TASK #3 Call the rectangleArea method and // store the result in the value variable

System.out.println("The area of the " + "rectangle is " + value); break; case 3: System.out.print("Enter the height of " + "the triangle: "); height = keyboard.nextDouble(); System.out.print("Enter the base of " + "the triangle: "); base = keyboard.nextDouble();

// TASK #3 Call the triangleArea method and // store the result in the value variable

System.out.println("The area of the " + "triangle is " + value); break; case 4: System.out.print("Enter the radius of " + "the circle: "); radius = keyboard.nextDouble();

// TASK #3 Call the circleCircumference method and // store the result in the value variable

System.out.println("The circumference " + "of the circle is " + value); break; case 5: System.out.print("Enter the length of " + "the rectangle: "); length = keyboard.nextDouble(); System.out.print("Enter the width of " + "the rectangle: "); width = keyboard.nextDouble();

// TASK #3 Call the rectanglePerimeter method and // store the result in the value variable

System.out.println("The perimeter of " + "the rectangle is " + value); break; case 6: System.out.print("Enter the length of " + "side 1 of the " + "triangle: "); side1 = keyboard.nextDouble(); System.out.print("Enter the length of " + "side 2 of the " + "triangle: "); side2 = keyboard.nextDouble(); System.out.print("Enter the length of " + "side 3 of the " + "triangle: "); side3 = keyboard.nextDouble();

// TASK #3 Call the trianglePerimeter method and // store the result in the value variable

System.out.println("The perimeter of " + "the triangle is " + value); break; default: System.out.println("You did not enter " + "a valid choice."); } keyboard.nextLine(); // Consume the new line

System.out.println("Do you want to exit " + "the program (Y/N)?: "); String answer = keyboard.nextLine(); letter = answer.charAt(0);

} while(letter != 'Y' && letter != 'y'); }

// TASK #1 Create the printMenu method here // TASK #2 Create the value-returning methods here // TASK #4 Write javadoc comments for each method }