Add logic to the drive method so that it throws an IllegalArgumentException if there aren't enough bars to support the l

Question

HELP ME!

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;
  }
}

Answer 1 · 2017-02-16T21:39:39Z

February 16, 2017 9:39pm

So, let's name what the problem with the drive() method is. We know that driving 1 lap is supposed to expend 1 bar of energy. The problem is, the drive method will allow us to drive more laps then we have energy for! that's not how the real world works, right? we want to model our code GoKart to work as closely as possible to real life. That means, we should not allow the drive method to drive a number of laps that is greater than our bars of energy stored in barCount. If someone tries to do that, we want an error to occur.

so how do we check if a condition is met, or in other words, how can we check if the number of laps to drive is greater than the number of bars in barCount? Sounds like it might be an if statement...

public void drive(int laps) {
    if (laps > barCount) {
       //put code here to execute when the laps driven is greater than the bars in barCount
    }
}

Great! now we have a codeblock that runs if the laps driven is greater than the bar count. But what code should we run there? well, the instructions say to throw an IllegalArgumentException. you can read up on that here. https://docs.oracle.com/javase/8/docs/api/java/lang/IllegalArgumentException.html

Lets try that.

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

Booyah! It works.

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Armando Escarcega

Armando Escarcega

Add logic to the drive method so that it throws an IllegalArgumentException if there aren't enough bars to support the l

1 Answer

Joseph Wasden

Joseph Wasden