Accessing List from another Class

Question

How can i add one array to another from two separate classes, then access it from the main class? The total list shows [] when printed, but the second class shows all the names.

public class Main {

    private static Plane fly = new Plane();
    private static Secondclass sec = new Secondclass();

    public static void main(String[] args) {

        sec.addPassenger("John");
        sec.addPassenger("Fatso");
        sec.addPassenger("Lisa");
        sec.addPassenger("Mike");
        sec.addPassenger("Randy");
        sec.addPassenger("Jonathan");

        System.out.println("Total list is "+fly.getTotalList());
        System.out.println("Second class is " + sec.getPassengerNames());
    }
}
________________________________________

public class Plane {
    private Secondclass sec;
    private ArrayList<String> totalList;

    public Plane() {
        this.totalList = new ArrayList<String>();
    }

    public void addTotalList() {
        this.totalList.addAll(sec.getPassengerNames());
    }

    public ArrayList<String> getTotalList() {
        return totalList;
    }

}
________________________________________

public class Secondclass{
    private ArrayList<String> passengerNames;

    public Secondclass() {
        this.passengerNames = new ArrayList<String>();
    }

    public ArrayList<String> getPassengerNames() {
        return passengerNames;
    }

    public void addPassenger(String name){
        passengerNames.add(name);
    }
}      

Answer 1

Two important lines are missing in your code.

• Write a constructor Plane with a reference of the object SecondClass as argument.
• Create a constructor with the sec object passed as argument after adding the values in the sec object.

• Call the plane.addTotalList()

   import java.util.ArrayList; public class Main { private static Plane fly; private static Secondclass sec = new Secondclass(); public static void main(String[] args) { sec.addPassenger("John"); sec.addPassenger("Fatso"); sec.addPassenger("Lisa"); sec.addPassenger("Mike"); sec.addPassenger("Randy"); sec.addPassenger("Jonathan"); fly = new Plane(sec); fly.addTotalList(); System.out.println("Total list is " + fly.getTotalList()); System.out.println("Second class is " + sec.getPassengerNames()); } } class Plane { private Secondclass sec; private ArrayList<String> totalList; public Plane(Secondclass sec) { this.sec = sec; this.totalList = new ArrayList<String>(); } public void addTotalList() { this.totalList.addAll(sec.getPassengerNames()); } public ArrayList<String> getTotalList() { return totalList; } } class Secondclass { private ArrayList<String> passengerNames; public Secondclass() { this.passengerNames = new ArrayList<String>(); } public ArrayList<String> getPassengerNames() { return passengerNames; } public void addPassenger(String name) { passengerNames.add(name); } }` 

  The output:

Total list is [John, Fatso, Lisa, Mike, Randy, Jonathan] Second class is [John, Fatso, Lisa, Mike, Randy, Jonathan]