Java Generic with ArrayList

by

ArrayList<? extends A> means an ArrayList of some unknown type that extends A.
That type might not be C, so you can’t add a C to the ArrayList.

In fact, since you don’t know what the ArrayList is supposed to contain, you can’t add anything to the ArrayList.

If you want an ArrayList that can hold any class that inherits A, use a ArrayList<A>.

More Related Contents:

  1. How do I find out what type each object is in a ArrayList?
  2. How do I clone a generic List in Java?
  3. new ArrayList() failing in Java
  4. Java generics – ArrayList initialization
  5. Why does the ArrayList implementation use Object[]?
  6. ArrayList Generic without Type
  7. ArrayList Data Structure – Daily Temperature
  8. I am new in using ArrayLists. Array Out of Bounds, Array seems to be empty, but have been adding Strings to it already
  9. What’s the reason I can’t create generic array types in Java?
  10. Instantiating a generic class in Java [duplicate]
  11. Deserialize a List object with Gson?
  12. Which Java Collection should I use?
  13. Generic array creation error
  14. Why won’t this generic java code compile?
  15. Why start an ArrayList with an initial capacity?
  16. Java: Detect duplicates in ArrayList?
  17. What is the difference between ? and Object in Java generics?
  18. Performance of traditional for loop vs Iterator/foreach in Java
  19. Difference between generic type and wildcard type
  20. How to get the last value of an ArrayList
  21. Firebase Firestore get data from collection
  22. Java – Removing duplicates in an ArrayList
  23. Creating new generic object with wildcard
  24. Generics with Spring RESTTemplate
  25. List
  26. How to create a custom deserializer in Jackson for a generic type?
  27. How to insert an object in an ArrayList at a specific position
  28. Removing Duplicate Values from ArrayList
  29. Java 8: Reference to [method] is ambiguous [duplicate]
  30. Cannot use Java 8 method with lambda arguments without specifying type arguments

Leave a Comment