LAB EXERCISE 4:  Mile per Gallon

Goal: In this exercise, you will learn how to:
1. Insert the Main Method (Main Entry Point to the Java Program)
2   Import a Java Class Library
3.  Create a Constructor which is a Special Method
4.  Create an Object
5.  Create a Method and call the Method

Program Specifications: Create a Java program that calculates a car’s gas mileage.  The formula for calculating the miles that a car can travel per gallon of gas is:

MPG = miles / gallons

The application should prompt the user to enter the miles the car can be driven on a full tank and the gallons of gas the car can hold.

A.  Pre-requisites:
1. Create a folder on your desktop Exercise-4

2. Launch Java EE- Eclipse
Note:  You will need to use the Java Perspective Workbench for this exercise

3. Setup your Eclipse Workspace to point to the Exercise-4 folder
a. Select File-> Switch Workspace
b. Browse and select your Exercie-4 folder as your Workspace.

B. Requirements to setup the Java Project:

1.  Create a Java Project and name it as MPGCalculator

2.  Create the first Class that will have the Main Method

a.       Name the Class as MainApp

b.       Choose the main method to insert into the class


3.  Create the second Class that will have the Constructor and Method

a.      Name the Class as Car

b.      Do not select the main method stub


C.  Requirements for the Car Class:

1.  Insert the import java.util.Scanner class which will allow data to be inputted from the console.

2.  Declare the Class variable carModel using a String data type

3.  Declare the Class variables- miles, gallons and MPG using a double data type

4.  Create the Constructor called Car

a.   Declare the scanner input class objects

b.   Prompt the user to input the data.

c.    Assign the inputted data to the variables

d.   Close the scanner input class objects

Below is the code you can copy and paste.

// declare the scanner object that will be used to input the miles
Scanner input1= new Scanner(;
System.out.println("Enter the car model: ");
carModel = input1.nextLine();  // assign the input value to the variable                       

// declare the scanner object that will be used to input the miles
Scanner input2= new Scanner(;
System.out.println("Enter the number of miles the car can be driven on a full tank: ");
miles = input2.nextDouble();  // assign the input value to the variable            

// declare the scanner object that will be used to input the gallons
Scanner input3= new Scanner(;
System.out.println("Enter gallons of gas the car can hold:  ");
gallons = input3.nextDouble();   // assign the input value to the variable

// close the scanner input objects

5.  Create the Method called calculateMPG

a.  Insert the formula   MPG= miles/ gallons;

b.  Insert return MPG;

Below is sample of the code:




























D. Requirements for the MainApp Class:

1.  Add comments (documentation)– Program Description, Author and Date

2.  Create the instance of object called model from the Car class

3.  Declare the mpg variable and assign the return value from the called object method – model.calculateMPG

4.  Display the calculated MPG value on the screen.


E. Test:  

1.   Save your Java code

2.   Compile and run your Java program.

3.   Verify there is no syntax, logical or run-time errors.

4.   Use the following set of test data to determine if the application is calculating properly:

Miles        Gallons    Miles per Gallon
375          10            37.50

289          12            24.08

190          15            12.67      


F. Submit your exercise in the Canvas Lab Exercise #4 Drop Box.

1. Submit the screen shot of the Eclipse Workbench window showing the Console output screen.
You can use Paint (save as JPG) or Word to paste the screenshot.

2. Zip up and submit the compressed MPGCalculator subfolder that is in the Exercise-04 folder.
NOTE: Right click on the
subfolder and select Send to “Compress Folder”.  The file will have a file extension of .zip.