6.7. Returning Objects¶
In many cases, your methods will need to return objects. This is really useful when we are creating Java programs that contain a ton of new classes. For example, let’s imagine that you were just hired by Goodreads to help maintain their database of books.
You begin by examining their Book class, which can be used to instantiate Book objects. While looking at the body of this class, you notice that there are a handful of methods that return String objects (open the Book.java file if you haven’t done so already!).
Pay attention to what all of these methods have in common – they all use String as their return type and they all contain the keyword return. In other words, the pattern that we followed in order to return primitive data types works for objects too!
Don’t worry, you will always follow this pattern when defining methods that return a value, no matter how complex it seems. For example, take a look at our Book class again; it now contains the awards attribute, which is an ArrayList of String objects.
If we wanted to define a method that returns the awards attribute of a Book object, we would write the following code:
public ArrayList<String> getAwards(){
return awards;
}
Notice that the return type of the getAwards method is ArrayList<String>. We chose this as our return type because the instance variable awards is an ArrayList of String objects. In other words, the return type must match the type of the value being returned, even if it is a really scary looking value.
If you have read “Stamped from the Beginning”, then you may know that this biography has won a few awards. However, you may have noticed that our program returns an empty ArrayList when the getAwards method is called. That’s not right! We must fix this!