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

Posted by Tinashe Nyaruwanga
Tinashe Nyaruwanga
525 Points

Throwing illegalArgumentException - Not enough battery

Here's my code - I thought I nailed it but I obviously did something wrong what is it?

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() { try{ drive(1); } catch (illegalArgumentException iae) {System.out.println("Not enough battery remains");
}

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

}

}

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

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

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

}

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() {
    try{ 
    drive(1);
    } catch (illegalArgumentException iae) {System.out.println("Not enough battery remains");  
  }


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

    }
  }

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

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

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

}

4 Answers

Craig Dennis
STAFF
Craig Dennis
Treehouse Teacher
Craig Dennis
Craig Dennis
Treehouse Teacher

Hi Tinashe!

You are super close! Remember you want to not modify the mBarsCount before using it. You might've accidentally did it, but you have mBarsCount -= laps. See how you have the -=? Try just minus.

Hope it helps!

ISAIAH S
ISAIAH S
1,409 Points

Hi Craig, I've completed the challenge with mBarsCount -= laps;.

Tinashe Nyaruwanga
Tinashe Nyaruwanga
525 Points
Tinashe Nyaruwanga
Tinashe Nyaruwanga
525 Points

Okay, I have removed my the equal sign and my code reads 

public void drive(int laps) {
       int newBarsCount = mBarsCount - laps;
    if (newBarsCount < mBarsCount) {
      throw new illegalArgumentException("Not enough battery remains"); 

      }
    }

its still not working? Am I missing something?

Craig Dennis
STAFF
Craig Dennis
Treehouse Teacher
Craig Dennis
Craig Dennis
Treehouse Teacher

So you want the exception to happen if the newBarsCount would be less than zero. And then you want to set the mBarsCount to the result stored in newBarsCount, so that you update the battery properly.

Jess Sanders
Jess Sanders
12,086 Points
Jess Sanders
Jess Sanders
12,086 Points 
  public void drive(int laps) {
    if (laps > mBarsCount) {
      throw new IllegalArgumentException("Not enough battery remains"); 
    }
    // Other driving code omitted for clarity purposes
    mBarsCount -= laps;

  }

You don't need the newBarsCount at all, really.