Why do I need to synchronize a list returned by Collections.synchronizedList

by

The list being synchronized only means that add, remove etc. operations are synchronized and therefore atomic. Iteration however is not and if a thread adds while another is iterating, you could get a ConcurrentModificationException.

By manually synchronizing your iteration block, you ensure that the list is not modified while iterating.

One alternative is to use a CopyOnWriteArrayList which provides an iterator that iterates over the list as it was known when the iteration started, regardless of subsequent modifications. That collection is however not very efficient if you need to change the content of the list very often.

More Related Contents:

  1. How do I make my ArrayList Thread-Safe? Another approach to problem in Java?
  2. How can I get my threaded program to print specific output
  3. Loop doesn’t see value changed by other thread without a print statement
  4. Avoid synchronized(this) in Java?
  5. Is multi-thread output from System.out.println interleaved
  6. Synchronizing on String objects in Java
  7. Synchronization vs Lock
  8. What is the difference between atomic / volatile / synchronized?
  9. How to synchronize a static variable among threads running different instances of a class in Java?
  10. How do synchronized static methods work in Java and can I use it for loading Hibernate entities?
  11. Are Java static initializers thread safe?
  12. Java double checked locking
  13. Java Synchronized Block for .class
  14. Java Singleton and Synchronization
  15. Printing Even and Odd using two Threads in Java
  16. Waiting on multiple threads to complete in Java
  17. Concurrent threads adding to ArrayList at same time – what happens?
  18. What is the difference between a synchronized method and synchronized block in Java? [duplicate]
  19. Correct way to synchronize ArrayList in java
  20. How to use invokeAll() to let all thread pool do their task?
  21. Sharing a variable between multiple different threads
  22. Should you synchronize the run method? Why or why not?
  23. Is synchronization within an HttpSession feasible?
  24. What is the difference between Thread.start() and Thread.run()?
  25. Why use a ReentrantLock if one can use synchronized(this)?
  26. ArrayList initial capacity and IndexOutOfBoundsException [duplicate]
  27. How to efficiently remove all null elements from a ArrayList or String Array?
  28. ThreadLocal & Memory Leak
  29. How do I implement task prioritization using an ExecutorService in Java 5?
  30. Setting Ideal size of Thread Pool [duplicate]

Leave a Comment