This week's giveaway is in the EJB and other Java EE Technologies forum. We're giving away four copies of EJB 3 in Action and have Debu Panda, Reza Rahman, Ryan Cuprak, and Michael Remijan on-line! See this thread for details.
Hello Blanka, wellcome to the Ranch Thread safe means that it is safe for several threads call the methods of an object, because they are not going to be executed simultaneously. Imagine wanting to add an element at the same time an iterator is returned, or deleting other. Because the code in the methods of Vector and HashTable are synchonized. One thread would have to wait before entering a method that is "protected" (synchronized on) by the same lock that has been adquired by another thread. Read more on the Java Tutorial , and this Thinking in Java's chapter