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

Benjamin Ing
Benjamin Ing
910 Points
Posted by Benjamin Ing
Benjamin Ing
910 Points

syntax error

I have a syntax error and can't find where I went wrong

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
      newAmount =  mBarsCount -= laps;
    if(newAmount > mBarsCount)
    {
      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;
  }

}

1 Answer

Allan Clark
Allan Clark
10,810 Points
Allan Clark
Allan Clark
10,810 Points 
  public void drive(int laps) {
    // Other driving code omitted for clarity purposes
      newAmount =  mBarsCount -= laps;
    if(newAmount > mBarsCount)
    {
      throw new IllegalArgumentException("Not enough battery remains"); 
    }
    mBarsCount -= laps;
  }

The newAmount variable does not have a type. Also actually the newAmount variable is not needed, you set it to be the number of bars minus the laps then use it in the conditional. What this does is finds the amount of bars that will be left after the laps have been driven and then checks if that amount is less than what you started with (i.e. mBarsCount). This will always be true so it will always throw the exception. Instead we just want to check if the laps variable is more than the number of bars we have. It could look something like this:

  public void drive(int laps) {
    // Other driving code omitted for clarity purposes

    if(laps > mBarsCount)
    {
      throw new IllegalArgumentException("Not enough battery remains"); 
    }
    mBarsCount -= laps;
  }