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Java Java Objects Harnessing the Power of Objects Throwing Exceptions

Ludwing Najera
Ludwing Najera
4,596 Points
Posted by Ludwing Najera
Ludwing Najera
4,596 Points

I don't understand why this doesn't work

It keeps giving me this message: "Make sure you throw a new IllegalArgumentException if the requested amount of laps would make the battery less than zero." The IF statement in the Drive class is correct, right?

GoKart.java 
class GoKart {
  public static final int MAX_BARS = 8;
  private String color;
  private int barCount;
  private int lapsDriven;

  public GoKart(String color) {
    this.color = color;
  }

  public String getColor() {
    return color;
  }
  public void charge() {
    barCount = MAX_BARS;
  }

  public boolean isBatteryEmpty() {
    return barCount == 0;
  }

  public boolean isFullyCharged() {
    return MAX_BARS == barCount;
  }

  public void drive() {
    drive(1);
  }

  public void drive(int laps) {
    lapsDriven += laps;
    barCount -= laps;
     if (laps >= MAX_BARS) {
      throw new IllegalArgumentException("Not enough bars!");
    }
  }
}

1 Answer

andren
andren
28,558 Points
andren
andren
28,558 Points

There are a couple of issues with the code:

  1. You are comparing laps against MAX_BARS instead of barCount. MAX_BARS contains the maximum bar value, not the current value, barCount is the variable used to store the current value.
  2. If I request 3 laps and there is 3 bars left then that is valid request, so laps being equal to barCount should not throw an exception. Meaning that you should be checking if laps is greater than barCount, not greater or equal to.
  3. Since your exception is meant to stop a lap from occurring it should be placed at the top of the method, not at the bottom.

If you fix those three issues like this:

public void drive(int laps) {
  if (laps > barCount) {
    throw new IllegalArgumentException("Not enough bars!");
  }
  lapsDriven += laps;
  barCount -= laps;  
}

Then your code will pass.