Difference between ArrayList, LinkedList and Vector

	ArrayList is in most cases what you want to use. It is a list backed by an array, which means it has fast access to each element via the get method. Vector is a leftover from the early days of Java, retrofitted with the List interface. The chief difference from ArrayList is that its methods are synchronized (ArrayList's are not). That means it is easier to use in multi-threaded environments, but it does incur the synchronization overhead. LinkedList is backed by a doubly-linked list, not an array. That means it's fast to access elements at the start and the end of the list, but less so in the middle. On the other hand, inserting and deleting elements is fast compared to ArrayList.  When to use ArrayList or LinkedList ? Ans)  Adding new elements is pretty fast for either type of list. For the ArrayList, doing  random lookup using "get" is fast, but for LinkedList, it's slow. It's slow because there's no efficient way to index into the middle of a linked list. When removing elements, using ArrayList is slow. This is because all remaining elements in the underlying array of Object instances must be shifted down for each remove operation. But here LinkedList is fast, because deletion can be done simply by changing a couple of links. So an ArrayList works best for cases where you're doing random access on the list, and a LinkedList works better if you're doing a lot of editing in the middle of the list.  Source : Read More - from java.sun ArrayList Now for some implementation notes. The ArrayList is actually encapsulating an actualy Array, an Object[]. When you instanciate ArrayList, an array is created, and when you add values into it, the array changes its size accordingly. This gives you strengths and weaknesses: Fast Random Access You can perform random access without fearing for performence. Calling get(int) will just access the underlying array. Adding values might be slow When you don’t know the amount of values the array will contain when you create it, a lot of shifting is going to be done in the memory space when the ArrayList manipulates its internal array. Slow manipulation When you’ll want to add a value randomly inside the array, between two already existing values, the array will have to start moving all the values one spot to the right in order to let that happen. LinkedList The LinkedList is implemented using nodes linked to each other. Each node contains a previous node link, next node link, and value, which contains the actual data. When new data is inserted, a node is inserted and the links of the surrounding nodes are updated accordingly. When one is removed, the same happens – The surrounding nodes are changing their links and the deleted node is garbage collected. This, as well, gives strengths and weaknesses: Fast manipulation As you’d expect, adding and removing new data anywhere in the list is instantanious. Change two links, and you have a new value anywhere you want it. No random access Even though the get(int) is still there, it now just iterates the list until it reaches the index you specified. It has some optimizations in order to do that, but that’s basically it. Some Conclusions ArrayList is very useful when a well defined set of data is needed in a List interface as opposed to an array. It can be dynamically changed, but try not to do so frequently throughout the life of the application. LinkedList is there for you to do just that: Manipulating it is very easy, and as long as its used for iteration purposes only and not for random accessing, it’s the best solution. Further, if you need random accessing from time to time, I suggest toArray for that specific moment. Another point I didn’t raise here is the Queue issue. LinkedList implements extended abilities to the normal List interface which allows it to add and remove elements from its beginning and end. This makes the LinkedList perfect for Queue and Stack purposes – Although in Java 5 they already added a Stack class. Hope this helped someone. Tell me if you want to differ.