Ты не инициализировал в классе Human поле children значением new ArrayList<>().
package com.javarush.task.task29.task2909.car;
import java.util.Date;
public class Car {
static public final int TRUCK = 0;
static public final int SEDAN = 1;
static public final int CABRIOLET = 2;
double fuel;
public double summerFuelConsumption;
public double winterFuelConsumption;
public double winterWarmingUp;
private int type;
private boolean driverAvailable;
private int numberOfPassengers;
public Car(int type, int numberOfPassengers) {
this.type = type;
this.numberOfPassengers = numberOfPassengers;
}
public int fill(double numberOfLiters) {
if (numberOfLiters < 0)
return -1;
fuel += numberOfLiters;
return 0;
}
public double getTripConsumption(Date date, int length, Date SummerStart, Date SummerEnd) {
double consumption;
if (date.before(SummerStart) || date.after(SummerEnd)) {
consumption = length * winterFuelConsumption + winterWarmingUp;
} else {
consumption = length * summerFuelConsumption;
}
return consumption;
}
public int getNumberOfPassengersCanBeTransferred() {
if (!isDriverAvailable())
return 0;
if (fuel <= 0)
return 0;
return numberOfPassengers;
}
public boolean isDriverAvailable() {
return driverAvailable;
}
public void setDriverAvailable(boolean driverAvailable) {
this.driverAvailable = driverAvailable;
}
public void startMoving() {
if (numberOfPassengers > 0) {
fastenPassengersBelts();
fastenDriverBelt();
} else {
fastenDriverBelt();
}
}
public void fastenPassengersBelts() {
}
public void fastenDriverBelt() {
}
public int getMaxSpeed() {
if (type == TRUCK)
return 80;
if (type == SEDAN)
return 120;
return 90;
}
}