Exercise 2 w/ Solution

25/07/2009 14:30


-load : double

-maxLoad : double

+Vehicle(max_Load : double)

+getLoad( ) : double

+getMaxLoad( ) : double

+addBox(weight : double) :boolean


  1. To solve the problem from the previous exercise, you hide the internal data(load and maxLoad) and provide a method, addBox, to perform the proper checking that the vehicle is not being overloaded.
  2. Copy your code from the last exercise, and modify if to implement the Vehicle class as shown in the above UML diagram.
    1. Modify the load and maxLoad attributes to be private.
    2. Add the addBox method. This method takes a single argument, which is the weight of the box in kilograms. The method must verify that adding the box will not violate the maximum load. If a violation occurs, the box is rejected by returning the value of false; otherwise the weight of the box is added to the vehicle load and the method returns true.

Hint: You must use an “if” statement. Here is the basic form f the conditional form:


If ( ) {


} else {




All of the data is assumed to be in kilograms.

    1. Read the TestVehicle.java code. The code cannot modify the load attribute directly, but now must use the addBox method. This method returns a true or false value, which is printed to the screen.
    2. Compile the Vehicle and TestVehicle classes.
    3. Run the TestVehicle class. The output generated should be:


Creating a vehicle with a 10,000kg maximum load.

Add box #1 (500kg) : true

Add box #2 (250kg) : true

Add box #3 (5000kg) : true

Add box #4 (4000kg) : true

Add box #5 (300kg) : false

Vehicle load is 9750.0 kg.





TestVehicle Part.

public class TestVehicle {
  public static void main(String[] args) {

    // Create a vehicle that can handle 10,000 kilograms weight
    System.out.println("Creating a vehicle with a 10,000kg maximum load.");
    Vehicle vehicle = new Vehicle(10000.0);

    // Add a few boxes
    System.out.println("Add box #1 (500kg) : " + vehicle.addBox(500.0));
    System.out.println("Add box #2 (250kg) : " + vehicle.addBox(250.0));
    System.out.println("Add box #3 (5000kg) : " + vehicle.addBox(5000.0));
    System.out.println("Add box #4 (4000kg) : " + vehicle.addBox(4000.0));
    System.out.println("Add box #5 (300kg) : " + vehicle.addBox(300.0));

    // Print out the final vehicle load
    System.out.println("Vehicle load is " + vehicle.getLoad() + " kg");


Vehicle Part.

public class Vehicle {
private double load, maxload;

public Vehicle ( double max_load){
maxload = max_load;
public double getLoad () {
return load;
public double getMaxLoad(){
return maxload;
public boolean addBox(double weight)

if( load + weight >= maxload ){
    return true;
} else {

load = load + weight;
    return false;