Whats the default 1 mean?

class GoKart {
  public static final int MAX_BARS = 8;
  private String color;
  private int barCount;
  private int lapsDriven;

  public GoKart(String color) {
    this.color = color;
  }

  public String getColor() {
    return color;
  }

  public void charge() {
    barCount = MAX_BARS;
  }

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

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

  public void drive(){

  }

  public void drive(int numberofLaps) {
    lapsDriven++;
    barCount--;
    numberofLaps+=lapsDriven;
    numberofLaps-=barCount;
  }

}