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"

• BalusC: Check the syntax highlighting. class is a keyword.
• Jonathan Fingland: @BalusC you should make that an answer
• BalusC: @Jonathan: that would have been an incomplete answer since I had to leave the computer :)
• Jonathan Fingland: @BalusC True. It would not have completely resolved the question. However, it might well have been the stumbling block for OP and identifying it may have been all that was needed. (Editing the answer to expand on it would still have been an option as well)

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();
}

• Mark Peters: @Jonathon: don't know why you deleted your answer; dependency injection is often a good idea in and of itself.
• lacas: its good, but i want more: Path path = null; if (thepath==0) path=new LinearPath(from, to); if (thepath==1) path=new CurvePath(from, to); this error again..
• Mark Peters: @lacas: Update your question in a clear manner. I don't understand you.
• Jonathon Faust: it was pretty much a mirror of yours and yours was a bit more complete. And a minute earlier than mine.