您的 Garage 应该具有 toString()的实现，该实现使用 ArrayList#toString()实现:

Your Garage should have the implementation of toString() which uses ArrayList#toString() implementation:

public String toString() {
    return "Garage: " + myGarage.toString();
}

还记得在 Cars.java 中实现 toString().

public String toString() {
    return "[" + this.carID + " " + 
    this.plateNum + " " +
    Cars.position + " " +
    Cars.assignedTo.toString + " " +
    String.valueOf(this.currTime) + "]"
}