来自另一个类的Java链表访问

Question

This code works great but I need to be able to add a type of car from another class by calling a method or something, I am really new to java and I'm guessing its a really easy fix but I've had a look around and tried a few things without any luck. So for example a class called addCar could access the linked list either in the main method or if i need to put the list in a separate class.

public static void main(String[] args) {
    LinkedList<String> cars;
    cars = new LinkedList<>();
    cars.add("SUV");
    Iterator<String> itr = cars.iterator();
    while (itr.hasNext()) {
         System.out.println(itr.next());}
    }
}

Answer 1

You can declare LinkedList<String> cars as a member of the class, then define a method where inside you can add the string you have as parameter like

public void addCar(String car){
    cars.add(car);
}

Answer 2

You can create the Car class as shown below:

public class Car {

   private LinkedList<String> cars = new LinkedList<>();

   public void addCar(String car) {
      cars.add(car);
   }

   public Iterator<String> iterator() {
      return cars.iterator();
    }
 }

One important point is that from the above code, you have defined what a Car is, but you did not create any cars ie, car objects.

So, if you have to create a car inside the main() , you need to use new operator (like new Car() ) and access the methods (like addCar etc..) of the car object as shown below:

public class YourTestClass {

    public static void main(String[] args) {
        Car car = new Car();
        car. addCar("SUV");
        Iterator<String> itr = car.iterator();
        while (itr.hasNext()) {
             System.out.println(itr.next());}
        }
    }
}

Answer 3

You can do something like this:

import java.util.LinkedList;

public class Test {
    static class SomeClass {
        LinkedList<String> cars;

        public SomeClass() {
            cars = new LinkedList<>();
            cars.add("SUV");
        }

        public void addType(String type) {
            cars.add(type);
        }

        public LinkedList<String> getCars() {
            return cars;
        }
    }

    public static void main(String[] args) {
        SomeClass someClass = new SomeClass();
        someClass.addType("Sedan");
        //or
        someClass.getCars().add("Hatchback");
        System.out.println( someClass.getCars() );
        //[SUV, Sedan, Hatchback]
    }
}