Steps of Working of Vector:

• Below are the steps of working of Vector in Java:
  1. Creation of Vector:
     • A new Vector can be created using:
       Vector<String> vector = new Vector<>();
     • When a Vector is created without specifying capacity, its default capacity is 10.
     • Initially, the size of the Vector is 0 (no elements added yet).
       Size = 0, Capacity = 10
  2. Adding Elements to the Vector:
     • Elements can be added using the add() method:
       vector.add(10);
vector.add(20);
vector.add(30);
vector.add(40);
     • Internally, elements are stored in a dynamic array (Object[] elementData). Each element occupies one index position.
     • Example internal structure:
       
  3. Automatic Resizing:
     • When the number of elements exceeds the current capacity, the Vector automatically increases its capacity.
     • The new capacity is calculated as:
       newCapacity = oldCapacity * 2 (i.e., it doubles its size).
     • Example:
       • Old Capacity → 10
       • New Capacity → 20
       A new internal array is created with the new capacity, and all old elements are copied into it.
     • The reference variable now points to the new array, while the old one becomes eligible for garbage collection.
  4. Accessing and Updating Elements:
     • Elements can be accessed using get(int index) and updated using set(int index, E element).
     • Since Vector uses an index-based array, both operations are very fast (O(1)).
     • Example:

       System.out.println(vector.get(1)); // prints 20
       vector.set(1, 222);
       System.out.println(vector);  // prints [10, 222, 30, 40]

  5. Thread-Safety (Synchronization):
     • All methods of Vector are synchronized, meaning only one thread can access it at a time.
     • This ensures thread-safety but may reduce performance compared to non-synchronized collections like ArrayList.
     • Example:

       Vector<Integer> v = new Vector<>();
       v.add(10);
       v.add(20);

  6. Traversal of Vector:
     • Vector can be traversed using Iterator, ListIterator, Enumeration, or an enhanced for-each loop.
     • Example:

       Enumeration<String> en = vector.elements();
       while (en.hasMoreElements())
       {
           System.out.println(en.nextElement());
       }

     • Enumeration is the legacy iterator introduced with Vector.

Vector is Good for:

1. Thread-safe operations (Synchronization):
   • All major methods in Vector are synchronized, making it thread-safe.
   • Suitable when multiple threads access and modify the same list concurrently.
2. Frequent read operations:
   • Provides fast access to elements using index-based retrieval (get(int index)).
   • Stores elements in a contiguous memory block like ArrayList, improving cache locality.
3. Automatic resizing:
   • When capacity is reached, Vector automatically increases its capacity by 100% (doubles it).
   • Ensures continuous storage without manual resizing.
4. Legacy system support:
   • Commonly used in older applications for backward compatibility with pre–JDK 1.2 code.

Vector is Not Good for:

1. Poor performance in single-threaded environments:
   • Synchronization introduces unnecessary overhead when thread safety is not required.
   • ArrayList performs better in such scenarios.
2. Frequent insertions/deletions in middle:
   • Requires shifting elements after every insertion or removal — making it slower.
3. Memory overhead due to resizing:
   • When capacity doubles, unused memory may remain unutilized until elements fill it.
4. Obsolete compared to modern classes:
   • It is considered a legacy class and is largely replaced by ArrayList and CopyOnWriteArrayList.

Summary Table: