Your `Car` class has what I would consider deficiencies. 

The `make`, `model`, `year_of_production` and `carId` shouldn’t change after creating a car.  They should be `final`.   Attributes like the `price` (and colour and condition) of the car can change. 

Inconsistent usage of `this.`. The function `getCarID()` doesn’t need it. 

**Bug**: The method `setYear_of_production` doesn’t change the `yearsOld` member!!!  

The constructor uses a hard-coded `2018`.

The `yearsOld` member should not be a member at all, but a getter method which relies on the year of production and the current year.  If after putting cars on the list, a year goes by, the cars current don’t (and can’t) age!  If you haven’t learnt how to query the current year, at least use a parameter or a global static (volatile, not constant) value.