Java – ArrayList v/s Vector

September 4, 2016 SJ Collection 0

In this article, we will discuss difference between ArrayList and Vector classes in detail i.e; ArrayList v/s Vector

1. ArrayList v/s Vector:

ArrayList	Vector
ArrayList is introduced in the original collection framework in Java 1.2 version	Vector is a legacy class including Stack, Dictionary, HashTable & Properties and introduced in Java 1.0 version
ArrayList methods are non-synchronized	All legacy collection classes are synchronized, thus Vector is synchronized (i.e.; all methods of Vector class is synchronized)
As ArrayList is non-synchronized, hence it isn’t thread-safe. So, programmer need to handle thread-safety while working in multi-threaded environment	As Vectror is synchronized, hence it is thread-safe. So, no need to worry while working in multi-threaded environment, as only one thread get chance to work at any given time
This is comparatively faster as it is non-synchronized, as threads doesn’t require to obtain lock before operating on ArrayList	Performance-wise vector is slower comparing with ArrayList due to synchronization, as threads need to wait for their chance to operate on Vector object
ArrayList increases its size by 50% of current array, when its capacity exceeds	Vector increases its size by 100% of current array, when its capacity exceeds
Only Iterator is allowed to iterate item/elements inside ArrayList	Both Iterator & Enumeration can be used to iterate item/elements inside Vector
ArrayList can be converted into synchronized ArrayList using static utility methods of Collections class Collection.synchronizedList(arrayList);	No need to do that, as already Vector is synchronized by default

Q) When to use ArrayList ?

If performance is the factor while storing element/objects, then ArrayList is apt
But definitely extra precautions need to be taken while working with multil-threaded environment
Also, check how much extra space is required when List is full; if 50% of original size if required then ArrayList will fits the case perfectly

Q) When to use Vector ?

If we aren’t concerned with performance, but element/objects need to be accessed in thread-safe manner, then Vector is good choice
But performance will be a big hit, as every thread to need to wait to obtain lock before accessing vector element/objects
Here, size increase in 2 times the original size; so if there are more number of items to be added then Vector will fits the bill perfectly

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Happy Coding !!
Happy Learning !!

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