Steps of Working of Stack:

• Below are the steps of working of Stack in Java:
  1. Creation of Stack:
     • A new Stack can be created using:
       Stack<Integer> stack = new Stack<>();
     • When created, the Stack is empty and its size is 0.
     • Internally, Stack is implemented as a subclass of Vector, which uses a dynamic array to store elements.
     • Example internal structure (initially empty):
       Top → [ ]
  2. Pushing Elements onto the Stack:

     • Elements are added using the push() method:
       stack.push(10);
stack.push(20);
stack.push(30);
stack.push(40);
stack.push(50);
stack.push(60);
       
     • Each new element is placed on the top of the stack (Last-In-First-Out principle).

     
  3. Peeking at the Top Element:
     

     • The peek() method returns the top element without removing it.
       System.out.println(stack.peek()); // prints 60

     
  4. Popping Elements from the Stack:
     

     • The pop() method removes and returns the top element of the stack.
       int top = stack.pop(); // Removes 60
     • After popping, the top shifts to the next element below it.

     
  5. Searching Elements in the Stack:
     • The search() method returns position (1-based) of an element from the top of the stack.
       System.out.println(stack.search(20)); // returns 4 because 60 has been removed from stack
     • If the element is not found, it returns -1.
  6. Checking if Stack is Empty:
     • The empty() method checks whether the stack is empty.
       System.out.println(stack.empty()); // false
  7. Traversal of Stack:
     • Since Stack extends Vector, it can be traversed using Iterator or a for-each loop.
     • Example:

       for (Integer no : stack)
       {
           System.out.println(no);
       }

     • Elements will be printed from bottom to top order.

Stack is Good for:

1. Implementing LIFO (Last-In-First-Out) operations:
   • Stack follows the LIFO principle — the last element added is the first one removed.
   • Suitable for use cases like undo/redo operations, expression evaluation, and function call management.
2. Thread-safe operations:
   • Since Stack extends Vector, all its methods are synchronized.
   • Safe for multi-threaded environments where only one thread should modify the stack at a time.
3. Simple and quick element management:
   • Provides predefined methods like push(), pop(), peek(), and search() for managing stack elements.
   • Easy to use for educational purposes or small stack-based operations.
4. Legacy system support:
   • Used in older Java applications before the introduction of Deque and ArrayDeque.
   • Helpful when maintaining or upgrading legacy Java codebases.

Stack is Not Good for:

1. Poor performance in single-threaded environments:
   • Synchronization adds unnecessary overhead when thread safety isn’t required.
   • ArrayDeque is much faster for single-threaded stack operations.
2. Limited functionality:
   • The Stack class only supports basic stack operations (push, pop, peek, search).
   • Does not provide advanced concurrent features like ConcurrentLinkedDeque or BlockingDeque.
3. Obsolete compared to modern classes:
   • Considered a legacy class and largely replaced by Deque or ArrayDeque since Java 1.5.
   • Modern alternatives are faster and more flexible.
4. Sequential search performance:
   • The search() method performs a linear search (O(n)) starting from the top of the stack.
   • Inefficient for large stacks where random access is not supported.

Summary Table: