Java Objects IllegalArgumentException Challenge

Question

I can't figure out how to work this code right. Can someone please help me out?

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(barCount < 0){
    throw new IllegalArgumentException("Not enough bars for another lap!");
    }
  }
}

Answer 1 · 2017-02-15T01:18:39Z

February 15, 2017 1:18am

You are pretty close!

you are on the right track with your if statement, but we are more concerned if the barcount is going to be less then zero, and not so much if it already is, right? We really ought to compare the bar count to the number of laps attempted to drive, and then throw the exception BEFORE we actually register any laps driven or any bars of energy spent in our goKart.

So, if you change the if statement to compare the requested number of laps, and if you only increment our member variables of laps driven and bar count AFTER checking to make sure the number of laps can actually be driven, you've got a goKart even Mario would be proud to drive.

See the code below.

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

  public void drive(int laps) {
     if (barCount < laps) {
    throw new IllegalArgumentException();
    } else {
      drive(laps);
    }

    lapsDriven += laps;
    barCount -= laps;  
  }

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Allen Emejuobi

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Java Objects IllegalArgumentException Challenge

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