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Java Java Objects Harnessing the Power of Objects Throwing Exceptions

Posted by Michael Dinkins
Michael Dinkins
9,483 Points

java objects throwing exceptions

Bummer! Make sure you throw a new IllegalArgumentException if the requested amount of laps would make the battery less than zero.

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) throws IllegalArgumentException {
    lapsDriven += laps;
    barCount -= laps;
     if (barCount > 0) {
      throw new IllegalArgumentException();
    }
  }
}

1 Answer

Steve Hunter
Steve Hunter
57,712 Points

Hi Michael,

You want to capture the error first, then do the logic part of the drive method. What we're trying to catch is a situation where you don't have enough barCount to drive the number of laps requested. So, if barCount is less than laps, don't change any of the values because the kart won't drive anywhere, and throw the IllegalArgumentException().

Inside, drive(int laps) start with an if statement. Test if laps > barCount, if it is, throw the exception; else do the maths piece that's already in the method.

Here's what I came up with - I hope it helps and makes sense to you.

  public void drive(int laps) {
    if(laps > barCount){
      throw new IllegalArgumentException();
    } else {
      lapsDriven += laps;
      barCount -= laps;
    }
  }

Good luck!

Steve.

Steve Hunter
Steve Hunter
57,712 Points

P.S. the challenge passes with or without the throws IllegalArgumentException - I suspect having it in place is best practice. :smile: :+1: