Question

JAVA PROGRAMING - TESTING CLASSES AND INHERITANCE

Create two classes - a vehicle class and gasguzzler class. Neither classes have I/O. Use a test class as well.

Vehicle class has methods and properties that all vehicles have. This class has two properties - speed (rate of travel in miles per hour) and weight (in pounds)

Vehicle Class Public Methods:

Vehicle objects can be constructed 2 different ways: by specifying the weight and the speed, or by specifying the weight only in which case the speed defaults to 0.

There are accessor (getter) methods for both weight and speed. There are no setter methods.

The speedup method takes 1 parameter, the amount to increase speed by, and returns the new speed of the vehicle. The increase must be positive to have any affect.

The slowdown method takes 1 parameter, the amount to decrease the speed by, and returns the new speed of the vehicle – can not be negative. The decrease must be positive to have any affect.

The brake method sets the speed to 0, and returns nothing.

The momentum method returns the calculated momentum of the vehicle. The formula for calculating momentum is:
weight * 0.4536 * speed * 0.447

The toString method should return a string indicating the weight of the vehicle, the current speed of the vehicle, and the momentum of the vehicle. Each piece of information should appear on a line by itself.

The gasguzzler class INHERITS from the vehicle class.

The GasGuzzler class adds 2 properties that are common to all gas guzzlers – fuel capacity and current fuel level. These are private member variables.

gasguzzler public methods:

A GasGuzzler object can be constructed in two different ways:

Specify the weight, speed, fuel capacity, and fuel level

Specify the weight and the capacity (fuel level defaults to capacity value)

There are accessor methods for both properties.

The gasUp method takes 1 parameter, the amount of gas to add to the current fuel level. The parameter must be positive. The fuel level cannot exceed the capacity. This method returns the new fuel level.

The useGas method takes 1 parameter, the amount of gas to subtract from the fuel level. The amount must be positive. The fuel level cannot go below 0. This method returns the new fuel level.

The toString method overrides the Vehicle class version of this method. This method must call the Vehicle class version to get the string containing base class information. It must add to that string information about the fuel capacity and fuel level. Each piece of information should appear on a line by itself.

Create a test program which thoroughly tests both classes. Verify that all the methods of the base class work first. Then add test cases for the derived class.

Answer 1

// Output screen shot is attached at the end

package learning;

class Vehicle{
private double speed;
private double weight;

public Vehicle(double weight, double speed){
  this.weight = weight;
  this.speed = speed;
}

public Vehicle(double weight){
  this.weight = weight;
  this.speed = 0;
}

public double getSpeed() {
  return speed;
}

public double getWeight() {
  return weight;
}

public double speedup(double amount){
  if(amount <=0){
   return speed;
  }else{
   speed = speed + amount;
   return speed;
  }
}

public double slowdown(double amount){
  if((speed - amount) < 0){
   return speed;
  }else{
   speed = speed - amount;
   return speed;
  }
}


public void brake(){
  speed = 0;
}

public double momentum (){
  return weight * 0.4536 * speed * 0.447;
}

public String toString(){
  StringBuilder sb = new StringBuilder();
  sb.append("weight: ").append(weight).append("\n");
  sb.append("speed: ").append(speed).append("\n");
  sb.append("momentum: ").append(momentum()).append("\n");
  return sb.toString();
}
}

class GasGuzzler extends Vehicle{
double fuelCapacity;
double currentFuelLevel;

public GasGuzzler(double weight, double speed, double fuelCapacity, double currentFuelLevel){
  super(weight, speed);
  this.fuelCapacity = fuelCapacity;
  this.currentFuelLevel = currentFuelLevel;
}

public GasGuzzler(double weight, double fuelCapacity){
  super(weight);
  this.fuelCapacity = fuelCapacity;
  this.currentFuelLevel = fuelCapacity;
}

public double getFuelCapacity() {
  return fuelCapacity;
}

public double getCurrentFuelLevel() {
  return currentFuelLevel;
}

public double gasUp(double amount){
  if((currentFuelLevel + amount) > fuelCapacity){
   return currentFuelLevel;
  }else{
   currentFuelLevel = currentFuelLevel + amount;
   return currentFuelLevel;
  }
}

public double useGas(double amount){
  if((currentFuelLevel - amount) < 0){
   return currentFuelLevel;
  }else{
   currentFuelLevel = currentFuelLevel - amount;
   return currentFuelLevel;
  }
}

public String toString(){
  StringBuilder sb = new StringBuilder();
  sb.append(super.toString());
  sb.append("current fuel level: ").append(currentFuelLevel).append("\n");
  sb.append("capacity: ").append(fuelCapacity).append("\n");
  return sb.toString();
}
}

public class VehicleTest {

public static void main(String args[]){
  System.out.println("--------------- Testing Vehicle -------------------");
  Vehicle vh = new Vehicle(230.23, 150);
  
  System.out.println("Speed : " + vh.getSpeed());
  System.out.println("Weight: " + vh.getWeight());
  System.out.println("Momentum : " + vh.momentum());
  // Increasing the speed
  vh.speedup(23);
  System.out.println("After increasing the Speed, speed is" + vh.getSpeed());
  // slowing down the speed
  vh.slowdown(12);
  // Printing Vehicle Object
  System.out.println("After slowing Down , the speed is: " + vh.getSpeed());
  System.out.println("Vehicle Object is:");
  System.out.println(vh);
  
  // Testing GasGuzzler
  System.out.println("-----------Testing GasGuzzler -------------");
  GasGuzzler gasGuzzler = new GasGuzzler(120, 456);
  System.out.println("Speed: " + gasGuzzler.getSpeed());
  System.out.println("Weight: " + gasGuzzler.getWeight());
  System.out.println("FuelCapacity: " + gasGuzzler.getFuelCapacity());
  System.out.println("fuel Level: " + gasGuzzler.getCurrentFuelLevel());
  System.out.println("Increasing the speed");
  gasGuzzler.speedup(123);
  System.out.println("After increasing the speed, speed is" + gasGuzzler.getSpeed());
  gasGuzzler.gasUp(500);
  gasGuzzler.useGas(34);
  System.out.println("After using the Gas, fuel level " + gasGuzzler.getCurrentFuelLevel());
  System.out.println("Printing GasGuzzler Object");
  System.out.println(gasGuzzler);
  
}


}

sterminated> VehicleTest [Java Application] C:Javaljdk1.7.0_80%bin javaw.exe (02-Apr-2018 11:39:48 pm) Testing Vehicle Speed : 150.0 Weight: 230.23 Momentum 7002.1875924000005 After increasing the Speed, speed is173.0 After slowing Down , the speed is: 161.0 Vehicle Object is: weight: 230.23 speed 161.0 momentum: 7515. 681349176 Testing GasGuzzler Speed: 0.0 Weight 120.0 FuelCapacity: 456.0 fuel Level: 456. Increasing the speed After increasing the speed, speed is123.0 After using the Gas, fuel level 422.0 Printing GasGuzzler Object weight: 120.0 speed: 123.0 momentum: 2992.725792 current fuel level: 422.0 capacity: 456.0