Stacks

In the world of programming, a stack is a data structure that follows the Last-In-First-Out (LIFO) principle. It is similar to a stack of plates, where the last plate added is the first one to be taken off.

Stacks have two main operations: push() and pop(). The push() operation adds an element to the top of the stack, while the pop() operation removes the top element from the stack.

To implement a stack in Java, you can use the Stack class from the Java Collections framework. Here's an example:

1import java.util.Stack;
2
3public class Main {
4    public static void main(String[] args) {
5        Stack<String> stack = new Stack<>();
6
7        // Push elements into the stack
8        stack.push("apple");
9        stack.push("banana");
10        stack.push("cherry");
11
12        // Get the top element of the stack
13        String topElement = stack.peek();
14        System.out.println("The top element is: " + topElement);
15
16        // Remove elements from the stack
17        String poppedElement = stack.pop();
18        System.out.println("Popped element: " + poppedElement);
19
20        // Check if the stack is empty
21        boolean isEmpty = stack.isEmpty();
22        System.out.println("Is the stack empty? " + isEmpty);
23    }
24}

Make sure to import the Stack class from the java.util package.

Stacks have various applications in computer science and software development. They can be used for tasks such as:

• Evaluating expressions
• Parsing languages
• Implementing function calls and recursion
• Performing undo/redo operations
• Solving problems requiring the Last-In-First-Out behavior

Understanding the concept of stacks and their applications is fundamental to solving many programming questions and building efficient algorithms.

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class Main {

    public static void main(String[] args) {

        Stack<String> stack = new Stack<>();

​

        // Push elements into the stack

        stack.push("apple");

        stack.push("banana");

        stack.push("cherry");

​

        // Get the top element of the stack

        String topElement = stack.peek();

        System.out.println("The top element is: " + topElement);

​

        // Remove elements from the stack

        String poppedElement = stack.pop();

        System.out.println("Popped element: " + poppedElement);

​

        // Check if the stack is empty

        boolean isEmpty = stack.isEmpty();

        System.out.println("Is the stack empty? " + isEmpty);

    }

}