Car class in Java 2 private instance variables miles per gallon gallons of gas i

Question

Car class in Java

2 private instance variables

miles per gallon

gallons of gas in tank (initially equals 3.5)

4 public methods

constructor() method

- initializes all instance variables to required starting values

- takes one parameter (miles per gallon) from carTester

addGas() method

- increases the amount of gas

- takes one parameter from carTester, the amount of gas to add to the tank

- update instance variable

drive() method

- decreases the amount of gas in the tank

- takes one parameter from carTester, the distance in miles that was driven

- update instance variable

range() method

- calculates range, the number of miles the car can travel until the gas is empty

- no parameters

- does not update instance variables

- returns the calculated value to carTester

carTester:

public class CarTester
{
/**
* main() method
*/
public static void main(String[] args)
{
Car honda = new Car(30.0); // 30 miles per gallon
  
honda.addGas(9.0); // add 9 more gallons
honda.drive(210.0); // drive 210 miles
  
// print range remaining
System.out.println("Honda range remaining: " + honda.range());

Car toyota = new Car(26.0); // 26 miles per gallon
  
toyota.addGas(4.5); // add 4.5 more gallons
toyota.drive(150.0); // drive 150 miles
  
// print range remaining
System.out.println("Toyota range remaining: " + toyota.range());
}
}

Explanation / Answer

//Car.java
public class Car
{
  
   //private instance variables
   private double milesPergallon;
   private double gas;
  
  
   //Set default values for milesPergallon
   //and gas
   public Car()
   {
       milesPergallon=0;
       //set gas to 3.5
       gas=3.5;
   }
  
   //Parameter constructor to set milespergallon
   public Car(double milesPergallon)
   {
       this.milesPergallon=milesPergallon;
       gas=3.5;
   }
  
  
   //Add gas to instance variable
   public void addGas(double gas)
   {
       this.gas=this.gas+gas;
   }
  
   //calculate the remainging gas
   public void drive(double miles)
   {
       //Calculate the remainingmiles
       double remainingMiles
           =gas*milesPergallon-miles;
      
       //calculate gas in terms remaiingmiles
       gas=remainingMiles%milesPergallon;
   }
  
  
   //calculatea the remainingmiles before car gas is empty
   public double range()
   {
       double remainingMiles
       =gas*milesPergallon;
      
       return remainingMiles;
   }  
}//end of the Car

-----------------------------------------------------------------------------------------------------------------------------

/**The java program CarTester that creats two instances of Car
* with miles per gallon , and calls addGas and then calls drive
* method then calls the range method to print the number of
* miles the car can move before the gas is empty.*/
//CarTester.java
public class CarTester
{
   /**
   * main() method
   */
   public static void main(String[] args)
   {
       Car honda = new Car(30.0);      // 30 miles per gallon

       honda.addGas(9.0);              // add 9 more gallons
       honda.drive(210.0);             // drive 210 miles

       // print range remaining
       System.out.println("Honda range remaining: " + honda.range());

       Car toyota = new Car(26.0);      // 26 miles per gallon

       toyota.addGas(4.5);              // add 4.5 more gallons
       toyota.drive(150.0);             // drive 150 miles

       // print range remaining
       System.out.println("Toyota range remaining: " + toyota.range());
   }
}

--------------------------------------------------------------------------------------------------------------------------------------------

Sample Output:

Honda range remaining: 450.0
Toyota range remaining: 156.0

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