Cant Understand Challenge

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

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

  public String getColor() {
    return mColor;
  }

  public boolean chargeB() {
    boolean wasChargeB = false;
    if (!isBatteryEmpty()) {
      mBarsCount++;
      wasChargeB = true;
    }

    while (chargeB()) {
    System.out.println("Charging!");
    }
     return wasChargeB;
  }


  public void charge() {
    mBarsCount = MAX_ENERGY_BARS;

  }

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

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

}