What Is a Stack Data Structure in Java?

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Angela Bailey

What Is a Stack Data Structure in Java?

A stack is a fundamental data structure in computer science that follows the Last-In-First-Out (LIFO) principle. In simpler terms, it is like a stack of books where the last book placed on top is the first one to be removed.

The Anatomy of a Stack

A stack consists of two primary operations:

  • Push: This operation adds an element to the top of the stack.
  • Pop: This operation removes and returns the topmost element from the stack.

The elements in a stack are usually of the same data type. In Java, you can create a stack using either an array or a linked list. The choice depends on your specific requirements and preferences.

Working with Stack in Java

In Java, you can use the built-in java.util.Stack class to work with stacks. This class provides several methods for manipulating stacks:

  • push(element): Adds an element to the top of the stack.
  • pop(): Removes and returns the topmost element from the stack.
  • peek(): Returns the topmost element without removing it from the stack.
  • empty(): Checks if the stack is empty or not.
  • search(element): Searches for an element in the stack and returns its position relative to the top. Returns -1 if not found.

An Example: Reversing a String

One practical application of a stack is reversing a string. Let’s see how we can achieve this using Java:


import java.Stack;

public class StringReverser {
    public static String reverse(String input) {
        Stack<Character> stack = new Stack<>();
        
        for (char c : input.toCharArray()) {
            stack.push(c);
        }
        
        StringBuilder reversed = new StringBuilder();
        
        while (!stack.empty()) {
            reversed.append(stack.pop());
        }
        
        return reversed.toString();
    }
    
    public static void main(String[] args) {
        String original = "Hello, World!";
        String reversed = reverse(original);
        
        System.out.println("Original: " + original);
        System.println("Reversed: " + reversed);
    }
}

This example uses a stack to reverse the characters in a string. It pushes each character onto the stack and then pops them off one by one, resulting in the reversed string.

Conclusion

A stack data structure is an essential concept in Java and computer science. Understanding how stacks work and how to use them effectively can greatly enhance your programming skills and problem-solving abilities.

Remember to utilize the push, pop, and other methods provided by the java.Stack class to manipulate stacks in Java. Keep exploring different use cases of stacks to expand your knowledge further.

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