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Java Java Objects (Retired) Harnessing the Power of Objects Throwing Exceptions

Diego Marrs
Diego Marrs
8,243 Points
Posted by Diego Marrs
Diego Marrs
8,243 Points

Super confused.

I am completely lost on what i'm suppose to do here.

GoKart.java 
public class GoKart {
  public static final int MAX_BARS = 8;
  private String mColor;
  private int mBarsCount;

  public GoKart(String color) {
    mColor = color;
    mBarsCount = 0;
  }

  public String getColor() {
    return mColor;
  }

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

  public void drive(int laps) {
    // Other driving code omitted for clarity purposes
    mBarsCount -= laps;
  }

  public void charge() {
    while (!isFullyCharged()) {
      mBarsCount++;
    }
  }

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

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

}

Please help.

2 Answers

Rick Buffington
Rick Buffington
8,146 Points
Rick Buffington
Rick Buffington
8,146 Points

Okay, what it is trying to do is have you focus on the code that throws a new exception. We know from the videos that to throw an exception you use the following syntax:

throw new Exception();

So, we can assume that the solution is going to involve something similar. What they want you to do is evaluate whether or not subtracting laps from mBarsCount will make it less than 0. We know this because the guidance they give is "...if the requested number of laps cannot be completed on the current battery level." We can see from the code that 1 lap is the equivalent of 1 battery bar. So, if:

// Their current code does this:
mBarsCount -= laps;

// BUT, we will not be able to do that if:
mBarsCount - laps < 0   // <-- We can't possibly do this because we wouldn't have enough bars to complete the laps.

So, if laps is LESS THAN mBarsCount, the resulting number will be LESS than 0. That is the logic they want you to check for.

if (mBarsCount < laps) {
  // THROW THAT EXCEPTION
}

I didn't finish all of the code to give you a chance to try and understand what I am saying. If it doesn't make sense, let me know and I can assist further.

Jeremy Hill
Jeremy Hill
29,567 Points
Jeremy Hill
Jeremy Hill
29,567 Points

try this:

public class GoKart {
  public static final int MAX_BARS = 8;
  private String mColor;
  private int mBarsCount;

  public GoKart(String color) {
    mColor = color;
    mBarsCount = 0;
  }

  public String getColor() {
    return mColor;
  }

  public void drive() {

    drive(1);
  }

  public void drive(int laps) {
    // Other driving code omitted for clarity purposes
    if(mBarsCount < laps){
     throw new IllegalArgumentException("Not enough battery remains"); 
    }
    mBarsCount -= laps;
  }

  public void charge() {
    while (!isFullyCharged()) {
      mBarsCount++;
    }
  }

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

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

}