What are the differences between ArrayList and Vector

Question

What are the differences between the two data structures ArrayList and Vector  and where should you use each of them

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Vector is a broken class that is not threadsafe  despite it being  synchronized  and is only used by students and other inexperienced programmers   ArrayList is the go-to List implementation used by professionals and experienced programmers   Professionals wanting a threadsafe List implementation use a CopyOnWriteArrayList

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As the documentation says  a Vector and an ArrayList are almost equivalent   The difference is that access to a Vector is synchronized  whereas access to an ArrayList is not   What this means is that only one thread can call methods on a Vector at a time  and there s a slight overhead in acquiring the lock  if you use an ArrayList  this isn t the case   Generally  you ll want to use an ArrayList  in the single-threaded case it s a better choice  and in the multi-threaded case  you get better control over locking   Want to allow concurrent reads   Fine   Want to perform one synchronization for a batch of ten writes   Also fine   It does require a little more care on  your end  but it s likely what you want   Also note that if you have an ArrayList  you can use the Collections synchronizedList function to create a synchronized list  thus getting you the equivalent of a Vector

User · Answer

Basically both ArrayList and Vector both uses internal Object Array    ArrayList  The ArrayList class extends AbstractList and implements the List interface and RandomAccess  marker interface   ArrayList supports dynamic arrays that can grow as needed  It gives us first iteration over elements  ArrayList uses internal Object Array  they are created with an default initial size of 10  When this size is exceeded  the collection is automatically increases to half of the default size that is 15   Vector  Vector is similar to ArrayList but the differences are  it is synchronized and its default initial size is 10 and when the size exceeds its size increases to double of the original size that means the new size will be 20  Vector is the only class other than ArrayList to implement RandomAccess  Vector is having four constructors out of that one takes two parameters Vector int initialCapacity  int capacityIncrement  capacityIncrement is the amount by which the capacity is increased when the vector overflows  so it have more control over the load factor   Some other differences are

User · Answer

ArrayList is newer and 20-30  faster    If you don t need something explitly apparent in Vector  use ArrayList

User · Answer

There are 2 major differentiation s between Vector and ArrayList     Vector is synchronized by default  and ArrayList is not   Note   you can make ArrayList also synchronized by passing arraylist object to Collections synchronizedList   method  Synchronized means   it can be used with multiple threads with out any side effect  ArrayLists grow by 50  of the previous size when space is not sufficient for new element  where as Vector will grow by 100  of the previous size when there is no space for new incoming element    Other than this  there are some practical differences between them  in terms of programming effort    To get the element at a particular location from Vector we use elementAt int index  function  This function name is very lengthy  In place of this in ArrayList we have get int index  which is very easy to remember and to use  Similarly to replace an existing element with a new element in Vector we use setElementAt   method  which is again very lengthy and may irritate the programmer to use repeatedly  In place of this ArrayList has add int index  object  method which is easy to use and remember  Like this they have more programmer friendly and easy to use function names in ArrayList    When to use which one    Try to avoid using Vectors completely  ArrayLists can do everything what a Vector can do  More over ArrayLists are by default not synchronized  If you want  you can synchronize it when ever you need by using Collections util class  ArrayList has easy to remember and use function names    Note   even though arraylist grows by 100   you can avoid this by ensurecapacity   method to make sure that you are allocating sufficient memory at the initial stages itself   Hope it helps

User · Answer

ArrayList and Vector both implements List interface and maintains insertion order But there are many differences between ArrayList and Vector classes     ArrayList -   ArrayList is not synchronized  ArrayList increments 50  of current array size if number of element exceeds from its capacity  ArrayList is not a legacy class  it is introduced in JDK 1 2  ArrayList is fast because it is non-synchronized  ArrayList uses Iterator interface to traverse the elements    Vector -   Vector is synchronized  Vector increments 100  means doubles the array size if total number of element exceeds than its capacity  Vector is a legacy class  Vector is slow because it is synchronized i e  in multithreading environment  it will hold the other threads in runnable or non-runnable state until current thread releases the lock of object  Vector uses Enumeration interface to traverse the elements  But it can use Iterator also    See Also   https   www javatpoint com difference-between-arraylist-and-vector

User · Answer

Differences   Vectors are synchronized  ArrayLists are not  Data Growth Methods   Use ArrayLists if there is no specific requirement to use Vectors   Synchronization  If multiple threads access an ArrayList concurrently then we must externally synchronize the block of code which modifies the list either structurally or simply modifies an element  Structural modification means addition or deletion of element s  from the list  Setting the value of an existing element is not a structural modification   Collections synchronizedList is normally used at the time of creation of the list to avoid any accidental unsynchronized access to the list   Reference  Data growth  Internally  both the ArrayList and Vector hold onto their contents using an Array  When an element is inserted into an ArrayList or a Vector  the object will need to expand its internal array if it runs out of room  A Vector defaults to doubling the size of its array  while the ArrayList increases its array size by 50 percent   Reference

[java] What are the differences between ArrayList and Vector?

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