Java Vector and Stack: Synchronized Legacy Classes & Modern Replacements

Vector and Stack are legacy collection classes introduced in JDK 1.0 prior to the invention of the unified Collections Framework in JDK 1.2. They were subsequently retrofitted to implement the List interface.

1. The Vector Class

Vector is identical to ArrayList in functionality, with two crucial architectural differences:

• Synchronized: Almost every public method in Vector is declared with the synchronized keyword, imposing heavy locking penalties in single-threaded environments.
• Growth Rate: When capacity is exceeded, Vector doubles in size (100% growth / 2.0x), consuming significantly more RAM than ArrayList (50% growth / 1.5x).

2. The Stack Class (LIFO)

Stack models a Last-In, First-Out (LIFO) container. Elements are pushed onto the top of the stack and popped from the top:

import java.util.Stack;

public class StackDemo {
    public static void main(String[] args) {
        Stack<String> browserHistory = new Stack<>();

        // 1. push(): Adds to top of stack
        browserHistory.push("https://veewom.com");
        browserHistory.push("https://veewom.com/java/");
        browserHistory.push("https://veewom.com/java/vector-stack.htm");

        // 2. peek(): Inspects top without removing
        System.out.println("Currently Viewing: " + browserHistory.peek());

        // 3. pop(): Removes and returns top item
        System.out.println("Clicked Back: " + browserHistory.pop());
        System.out.println("Now Viewing:   " + browserHistory.peek());
    }
}