Java - Class Arrays

Understanding on how to create classes that holds arrays.

Cars / Class

package model;

import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlType;

@XmlType(propOrder = {"model", "type", "price"})
public class Cars{
    static Integer nextId = 0;
    private Integer id;
    private String model;
    private String type;
    private Integer price;

    public Cars(){
        this.id = nextId++;
    }

    public Cars(String model, String type, Integer price){
        this.id = nextId++;
        this.model = model;
        this.type = type;
        this.price = price;
    }

    public String getModel(){
        return model;
    }

    public void setModel(String model){
        this.model = model;
    }

    public String getType(){
        return type;
    }

    public void setType(String type){
        this.type = type;
    }

    public Integer getPrice(){ 
        return price;
    }

    public void setPrice(Integer price){
        this.price = price;
    }

    @XmlAttribute
    public Integer getId(){
        return id;
    }

    public void setId(Integer id){
        this.id = id;
    }

    @Override
    public String toString(){
        return "ID: " + id + ", Model: " + model + ", Type: " + type + ", Price: " + price;
    }
}

Inventory / Arrays

package model;

import java.util.ArrayList;
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
@XmlAccessorType(XmlAccessType.NONE)
public class Inventory{
    private ArrayList<Cars> inventory;

    public Inventory(){
        inventory = new ArrayList();
    }

    @XmlElement(name = "car")
    public ArrayList<Cars> getInventory(){
        return inventory;
    }

    public void add(Cars item){
        getInventory().add(0,item);
    }

    public int getSize(){
        return inventory.size();
    }

    public void setList(ArrayList<Cars> inv){
        this.inventory = inv;
    }
}