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

harnessing the power of objects

Okay, so let's throw an IllegalArgumentException from the drive method if the requested number of laps cannot be completed on the current battery level. Make the exception message "Not enough battery remains"

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;
  }

}

2 Answers

Jeroen de Vrind
Jeroen de Vrind
29,772 Points

In the drive() method you have to try to call the drive(int laps) method and catch any error when it occurs. In the drive(int laps) method you can add a check to see if the remaining battery power (mBarsCount) is enough to drive the laps. When it runs out of battery you have to throw an exception with a message. This exception and message are then watched in the drive() method where you can print the message out to the console.

public void drive() {
    try {
      drive(1);
    } catch(IllegalArgumentException iae) {
      System.out.println(iae);
    }
  }

  public void drive(int laps) {
    // Other driving code omitted for clarity purposes
    if (mBarsCount-laps<=0) {
      throw(new IllegalArgumentException("Not enough battery remains"));
    }

    mBarsCount -= laps;
  }

Try:

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 (laps > 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;
  }

}