how to save arraylist after the app is closed. This is my global class

public class GlobalClass extends Application {

ArrayList<Trip> allTrips = new ArrayList<>();

public ArrayList<String> allTripsString() {
    ArrayList<String> allTripsString = new ArrayList<String>();
    for (Trip trip : allTrips){
        allTripsString.add(trip.getName());
    }
    return allTripsString;
    }
}

This is my trip class

public class Trip {

/** A map with category as key and the associed list of items as value */
Map<String,List<Item>> expanses;

private String name;
public ArrayList<String> ExpensesCategory = new ArrayList<>();
public ArrayList<String> Adults = new ArrayList<>();
public ArrayList<String> Children = new ArrayList<>();
public ArrayList<String> ShoppingName = new ArrayList<>();
public ArrayList<Double> ShoppingPrice = new ArrayList<>();
public ArrayList<String> ShoppingCategory = new ArrayList<>();
public double budget = 0;

/** An item in the expanses list */
static class Item {
    final String name;
    final double cost;
    final String Category;
    public Item(String name, double cost, String Category) {
        this.name = name;
        this.cost = cost;
        this.Category = Category;
    }
    @Override public String toString() {
        return this.name + " (" + this.cost + "$)";
    }
    public String getName(){
        return name;
    }
    public String getCategory(){
        return Category;
    }
    public double getCost(){
        return cost;
    }
}

public Trip(String name) {
    this.name = name;
    this.expanses = new HashMap<String,List<Item>>();
    for (String cat: ExpensesCategory) { // init the categories with empty lists
        this.expanses.put(cat, new ArrayList<Item>());
    }
}

public String getName(){
    return name;
}

/** Register a new expanse to the trip. */
public void add(String item, double cost, String category) {
    List<Item> list = this.expanses.get(category);
    if (list == null)
        throw new IllegalArgumentException("Category '"+category+"' does not exist.");
    list.add( new Item(item, cost, category) );
}

/** Get the expanses, given a category.
 * @return  a fresh ArrayList containing the category elements, or null if the category does not exists
 */
public List<Item> getItems(String category) {
    List<Item> list = this.expanses.get(category);
    if (list == null)
        return null;
    return new ArrayList<Item>(list);
}

/** Get the expanses, given a category.
 * @return  a fresh ArrayList containing all the elements
 */
public List<Item> getItems() {
    List<Item> list = new ArrayList<Item>();
    for (List<Item> l: this.expanses.values()) // fill with each category items
        list.addAll(l);
    return list;
}

public ArrayList<String> getItemsString() {
    List<Item> list = new ArrayList<Item>();
    for (List<Item> l: this.expanses.values()) // fill with each category items
        list.addAll(l);
    ArrayList<String> listString = new ArrayList<String>();
    for (Item item : list){
        listString.add(item.getName());
    }
    return listString;
}

public ArrayList<Double> getItemsCost(){
    List<Item> list = new ArrayList<Item>();
    for (List<Item> l: this.expanses.values()) // fill with each category items
        list.addAll(l);
    ArrayList<Double> listDouble = new ArrayList<>();
    for (Item item : list){
        listDouble.add(item.getCost());
    }
    return listDouble;
}

public ArrayList<String> getItemsCategory() {
    List<Item> list = new ArrayList<Item>();
    for (List<Item> l: this.expanses.values()) // fill with each category items
        list.addAll(l);
    ArrayList<String> listString = new ArrayList<String>();
    for (Item item : list){
        listString.add(item.getCategory());
    }
    return listString;
}

/** Get the total cost, given a category. */
public double getCost(String category) {
    List<Item> list = this.expanses.get(category);
    if (list == null)
        return -1;
    double cost = 0;
    for (Item item: list)
        cost += item.cost;
    return cost;
}

/** Get the total cost. */
public double getCost() {
    double cost = 0;
    for (List<Item> l: this.expanses.values())
        for (Item item: l)
            cost += item.cost;
    cost *= 1000;
    cost = (int)(cost);
    cost /= 1000;
    return cost;
    }
}

I want to save the array list and when I close and open the app the array list (alltrips) is saved. How to do this?

I want to use shared preferences but I don't know how to do this because it is not a string it array list with Trip. Can anyone help me to save the arraylist in shared preferences?