What Is Stack Data Structure in Java?


Heather Bennett

The stack data structure is a fundamental concept in computer science and is widely used in various programming languages, including Java. It is a last-in, first-out (LIFO) data structure, meaning that the last element added to the stack will be the first one to be removed.

Stack Operations

In Java, the stack data structure is implemented using the java.util.Stack class. This class provides several methods to perform operations on the stack:

  • push(element): This method adds an element to the top of the stack.
  • pop(): This method removes and returns the topmost element from the stack.
  • peek(): This method returns the topmost element of the stack without removing it.
  • isEmpty(): This method checks whether the stack is empty or not.

The following code snippet demonstrates how to create a stack and perform basic operations:

import java.Stack;

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

        // Pushing elements into the stack

        // Popping elements from the stack
        String element1 = stack.pop();
        String element2 = stack.pop();

        System.out.println("Popped elements: " + element1 + ", " + element2);
        // Peeking at the topmost element
        String topElement = stack.peek();
        System.println("Top element: " + topElement);
        // Checking if the stack is empty
        boolean empty = stack.isEmpty();
        System.println("Is stack empty? " + empty);

Use Cases of Stack

The stack data structure has various practical use cases in software development. Here are a few examples:

1. Function Call Stack

When a function is called, the program stores its return address and local variables in a stack frame. This allows the program to keep track of the function calls and return to the appropriate location after each function call is completed.

2. Undo/Redo Operations

In many applications, such as text editors or graphic design tools, the stack can be used to implement undo and redo operations. Each action performed by the user is stored as a command in the stack, allowing them to undo or redo previous actions.

3. Evaluation of Expressions

The stack data structure is commonly used to evaluate expressions, especially arithmetic expressions. By using stacks, we can convert infix expressions into postfix or prefix notation and then evaluate them efficiently.

In conclusion, understanding the stack data structure is crucial for any Java developer. It provides an efficient way to store and retrieve elements in a last-in, first-out manner. By using the java.Stack class and its methods, you can easily implement stacks in your Java programs and leverage their power for solving various problems.

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