Java: Avoid inserting duplicate in arraylist

by

Whenever you want to prevent duplicates, you want to use a Set.

In this case, a HashSet would be just fine for you.

HashSet karSet = new HashSet();
karSet.add(foo);
karSet.add(bar);
karSet.add(foo);
System.out.println(karSet.size());
//Output is 2

For completeness, I would also suggest you use the generic (parameterized) version of the class, assuming Java 5 or higher.

HashSet<String> stringSet = new HashSet<String>();
HashSet<Integer> intSet = new HashSet<Integer>();
...etc...

This will give you some type safety as well for getting items in and out of your set.

More Related Contents:

  1. How does array work? How to create a basic array data structure using java? [closed]
  2. How to implement a tree data-structure in Java?
  3. How do I remove objects from an array in Java?
  4. JTable design to synchronize with back-end data-structure
  5. HashMap get/put complexity
  6. How to convert List to Map?
  7. How to print binary tree diagram in Java?
  8. Calculate size of Object in Java [duplicate]
  9. How to implement a Map with multiple keys? [duplicate]
  10. How to detect a loop in a linked list?
  11. How would you implement an LRU cache in Java?
  12. Reversing a linked list in Java, recursively
  13. Stack with find-min/find-max more efficient than O(n)?
  14. Why should I use Deque over Stack?
  15. Data structures that can map a range of keys to a value
  16. What are the time complexities of various data structures?
  17. How can CopyOnWriteArrayList be thread-safe?
  18. Why doesn’t java.util.Set have get(int index)?
  19. Sample Directed Graph and Topological Sort Code [closed]
  20. When to use a List over an Array in Java?
  21. LRU cache in Java with Generics and O(1) operations
  22. Automatically sorted by values map in Java
  23. How to restore the PriorityQueue to its initial state before the method call?
  24. How to determine if binary tree is balanced?
  25. LinkedBlockingQueue vs ConcurrentLinkedQueue
  26. Hash : How does it work internally?
  27. Creating a LinkedList class from scratch
  28. Table like java data structure
  29. Finding the shortest path nodes with breadth first search
  30. Does java have a “LinkedConcurrentHashMap” data structure?

Leave a Comment