Difference Between Arraylist And Vector : Core Java Interview Collection Question

た入场券 2022-03-29 07:52 126阅读 0赞

Difference between Vector and Arraylist is the most common Core Java Interview question you will come across in Collection . This question is mostly used as a start up question by the Interviewers before testing deep roots of the Collection .  
Vector , ArrayList classes are implemented using dynamically resizable array providing fast random access and fast list traversal very much like using an ordinary array . ArrayList support dynamic arrays that can grow as needed that is ArrayList can be dynamically increased or decreased in size .  
  
  
***Read Also :*** [Difference between HashMap and ConcurrentHashMap][]  
  
  
**Arraylist vs Vector in Java**  
  
  
**1. Synchronization and Thread-Safe**  
  
**Vector is synchronized while ArrayList is not synchronized .** Synchronization and thread safe means at a time only one thread can access the code .In Vector class all the methods are synchronized .Thats why the Vector object is already synchronized when it is created .  
  
**2. Performance**  
  
**Vector is slow as it is thread safe . In comparison ArrayList is fast** as it is non synchronized . Thus in ArrayList two or more threads can access the code at the same time , while Vector is limited to one thread at a time.  
  
**3. Automatic Increase in Capacity**  
  
**A Vector defaults to doubling size of its array .** While when you insert an element into the ArrayList ,  **it increases**  
**its Array size by 50% .**  
  
  
By default ArrayList size is 10 . It checks whether it reaches the last element then it will create the new array ,copy the new data of last array to new array ,then old array is garbage collected by the Java Virtual Machine (JVM) .  
  
**4. Set Increment Size**  
  
**ArrayList does not define the increment size . Vector defines the increment size .**  
  
You can find the following method in Vector Class  
  
public synchronized void setSize(int i) \{ //some code \}  
  
There is no setSize() method or any other method in ArrayList which can manually set the increment size.  
  
**5. Enumerator**  
  
**Other than Hashtable ,Vector is the only other class which uses both [Enumeration and Iterator][] .While ArrayList can only use Iterator for traversing an ArrayList .**  
  
**6. Introduction in Java**   
  
java.util.Vector class was there in java since the very first version of the java development kit (jdk).  
java.util.ArrayList was introduced in java version 1.2 , as part of Java Collections framework . In java version 1.2 , Vector class has been refactored to implement the List Inteface .  
  
  
Please do mention in the comments in case if you have any doubts or suggestions regarding the post.

[Difference between HashMap and ConcurrentHashMap]: http://javahungry.blogspot.com/2014/02/hashmap-vs-concurrenthashmap-java-collections-interview-question.html
[Enumeration and Iterator]: http://javahungry.blogspot.com/2013/06/difference-between-iterator-and-enumeration-collections-java-interview-question-with-example.html