Throw a new IllegalArgumentException?

Question

Hi, I don't understand what I have to do to throw a new IllegalArgumentException.

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(MAX_BARS < barCount){
    throw new IllegalArgumentException("No more bars!");
    }
  }
}

Answer 1 · 2017-12-04T00:23:06Z

December 4, 2017 12:23am

HI Lana

The way you throw you IllegalArgumentException is perfect. However, you made some mistakes on your IF statement. You need to check it there will be enough bars in the battery(barCount) to fulfill the whole laps requested by the user. Fortunately one laps will EXACTLY consume one barCount therefore IF the number of laps requested exceed the number barCount you need to throw your perfect IllegalArgumentException. One more note : please put the IF statement in the beginning of the method so it will validate the request before you actually given it to the process, This will be best practice from my point of view.

This is my example code:

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

I hope this can help

Welcome to the Treehouse Community

Looking to learn something new?

Lana Wong

Lana Wong

Throw a new IllegalArgumentException?

1 Answer

Yanuar Prakoso

Yanuar Prakoso