ArrayList Vs Vector in Java

Last Updated: 15 January, 2023

ArrayList and Vector are both classes of the Collection Framework, and both classes implement the List interface.

Both the classes have some common features, such as maintaining the insertion order of elements and containing duplicate elements, etc.

However, there are many differences between the ArrayList and Vector classes that are given below.

👉 ArrayList

ArrayList in Java is a concrete class of the List interface that was introduced in the JDK 1.2 version and is available in the java.util package. An ArrayList is used to store a dynamically sized collection of elements. An ArrayList grows in size automatically. Elements can be added, modified, and removed from an ArrayList whenever there is a need.

Java ArrayList Class Declaration

public class ArrayList<E>
extends AbstractList<E>
implements List<E>, RandomAccess, Cloneable, Serializable

Here, E defines the type of elements that the List will contain.

Java ArrayList important features:

ArrayList extends the AbstractList class and implements the List, RandomAccess, Cloneable, and Serializable interfaces.
ArrayList is an ordered collection, so it maintains the insertion order of the elements.
ArrayList allows duplicate and null elements.
By default, an ArrayList is not synchronized. If multiple threads try to modify an ArrayList at the same time, then the final outcome will be non-deterministic.
ArrayList does not accept primitive types like int, char, etc. We need to use boxed types like Integer, Character, Boolean, etc.
ArrayList allows random access because the array works on an index basis.
Each ArrayList instance has a capacity. The capacity is the size of the array used to store the elements in the list. The default capacity is 10.
ArrayList performance is a bit slower than LinkedList because a lot of shifting operations are needed if we insert or delete elements in the middle of the ArrayList.

👉 Vector

The Vector class was introduced in the Java 1.0 version and is available in the java.util package and implements the List interface. Vector is a synchronized and legacy class in Java.

A Vector is similar to an ArrayList in Java. A Vector is a dynamic array of objects which can grow or shrink in size as needed to accommodate adding and removing items after the Vector has been created.

The iterators returned by the Vector class are fail-fast. If the vector is structurally modified at any time after the iterator is created, in any way except through the iterator's own remove or add methods, the iterator will throw a ConcurrentModificationException.

Vector Class Declaration

public class Vector<E>
extends AbstractList<E>
implements List<E>, RandomAccess, Cloneable, Serializable

Here, E defines the type of elements that the List will contain.

Important features of Vector:

Vector underlying data structure is a resizable or growable array.
Vector accepts duplicate elements.
Vector maintains the insertion order of elements.
A 'null' insertion in Vector is possible.
Vector is by default synchronized.
Vector default capacity is 10.

👉 ArrayList and Vector have the following differences:

Comparison Parameters	ArrayList Vs Vector

Synchronization	ArrayList is not synchronized (not thread-safe), which means multiple threads can access an ArrayList object at the same time. Vector, on the other hand, is synchronised (thread-safe), so only one thread can access the vector object at a time.

Performance	ArrayList is faster since it is non-synchronized, whereas Vector is by default synchronized so its operations give slower performance.

Data Growth	ArrayList and Vector both grow and shrink dynamically to maintain optimal use of storage. ArrayList increases by 50% of the current array size if the number of elements exceeds its capacity, whereas Vector increases by 100%, essentially doubling the current array size.

Traversal	ArrayList can only use iterator to traverse its elements, whereas Vector can use both enumeration and iterator to traverse its elements.

Legacy Class	ArrayList was introduced in the JDK 1.2 version, and ArrayList is not a legacy class, whereas Vector is a legacy class. It was introduced in the JDK 1.0 version.

👉 Example of ArrayList and Vector in Java

Example 1: A sample Java program of ArrayList

  import java.util.ArrayList;
  class ArrayListExample {
    public static void main(String[] args){
      // Creating ArrayList
      ArrayList<String> countries = new ArrayList<>();
      // Adding elements in ArrayList
      countries.add("India");
      countries.add("Canada");
      countries.add("US");
      countries.add("England");
      // Printing ArrayList elements
      System.out.println("ArrayList Elements: " + countries);
    }
  }

Output

ArrayList Elements: [India, Canada, US, England]

Example 2: A sample Java program of Vector

  import java.util.Vector;
  class VectorExample {
    public static void main(String[] args){
      // Creating Vector
      Vector<String> countries = new Vector<>();
      // Adding elements in Vector
      countries.add("India");
      countries.add("Canada");
      countries.add("US");
      countries.add("England");
      // Printing Vector elements
      System.out.println("Vector Elements: " + countries);
    }
  }

Output

Vector Elements: [India, Canada, US, England]

That's all guys, hope this Java article is helpful for you.

Happy Learning... 😀

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