Java interface question

Question

I have 2 classes

• classCurvePath
• classLinearPath

In these classes I have an items ArrayList.

How can I call a method like:

...
    if (i==1) method(classCurvePath);
    if (i==2) method(classLinearPath);

..    
    void method(Object class) {

    ArrayList al = class.items;

    }

Do I need an interface? How can I do this? This is not working: "cannot be resolved or not a field"

Answer 1

Yes you probably want an interface (maybe even an abstract class):

public interface Path {
   List<Item> getItems();
}

public class CurvePath implements Path {
   public List<Item> getItems() {
      //specific implementation for curved path, maybe
      return items;
   }
}

public class LinearPath implements Path {
   public List<Item> getItems() {
      //specific implementation for linear path
      return items;
   }
}


//...
void method(Path clazz) {

    ArrayList<Item> al = clazz.getItems();

}