Stack empty() Method in Java

The java.util.Stack.empty() method in Java is used to check whether a stack is empty or not. The method is of boolean type and returns true if the stack is empty else false. 

Syntax:

STACK.empty()

Parameters: The method does not take any parameters. 

Return Value: The method returns boolean true if the stack is empty else it returns false. 

Below programs illustrate the working of java.util.Stack.empty() method:

Program 1:

Java

// Java code to demonstrate empty() method
import java.util.*;

public class Stack_Demo {
    public static void main(String[] args)
    {

        // Creating an empty Stack
        Stack<String> STACK = new Stack<String>();

        // Stacking strings
        STACK.push("Geeks");
        STACK.push("4");
        STACK.push("Geeks");
        STACK.push("Welcomes");
        STACK.push("You");

        // Displaying the Stack
        System.out.println("The stack is: " + STACK);

        // Checking for the emptiness of stack
        System.out.println("Is the stack empty? " +
                                    STACK.empty());

        // Popping out all the elements
        STACK.pop();
        STACK.pop();
        STACK.pop();
        STACK.pop();
        STACK.pop();

        // Checking for the emptiness of stack
        System.out.println("Is the stack empty? " +
                                    STACK.empty());
    }
}

Output

The stack is: [Geeks, 4, Geeks, Welcomes, You]
Is the stack empty? false
Is the stack empty? true

Program 2:

Java

// Java code to demonstrate empty() method
import java.util.*;

public class Stack_Demo {
    public static void main(String[] args)
    {

        // Creating an empty Stack
        Stack<Integer> STACK = new Stack<Integer>();

        // Stacking int values
        STACK.push(8);
        STACK.push(5);
        STACK.push(9);
        STACK.push(2);
        STACK.push(4);

        // Displaying the Stack
        System.out.println("The stack is: " + STACK);

        // Checking for the emptiness of stack
        System.out.println("Is the stack empty? " +
                                    STACK.empty());
    }
}

Output

The stack is: [8, 5, 9, 2, 4]
Is the stack empty? false

Program 3:  How to travel through Stack using java.util.Stack.empty() method to get sum of all elements

Java

// Java code to demonstrate Traversal in Stack using empty() method
import java.util.*;

public class Stack_Demo {
    public static void main(String[] args)
    {

        // Creating an empty Stack
        Stack<Integer> STACK = new Stack<>();
        // You can also Initialize Stack as below
        // both are same way
        // Stack<Integer> STACK = new Stack<Integer>();

        // Stack Pushing Elements
        STACK.push(23);
        STACK.push(3);
        STACK.push(-30);
        STACK.push(13);
        STACK.push(45);

        // Displaying the Stack
        System.out.println("The stack is: " + STACK);

        // Initialize Sum Variable which will store sum of
        // all element
        int sum = 0;
        // Popping till Stack is Not Empty
        while (!STACK.empty()) {
            /* If stack have some elements then
             Stack.empty() will written false and ! of it
             will true so while will till !STACK.empty() it
             become false for this to be false STACK.empty()
             need to be true when STACK.empty() is true mean
             we have completely travel Stack*/
            sum += STACK.pop();
        }
        // Initialize
        System.out.println("The Sum Of Elements is " + sum);

        // Checking for the emptiness of stack
        System.out.println("Is the stack empty? "
                           + STACK.empty());
    }
      // This Code is Contributed By Vikas Bishnoi
}

Output

The stack is: [23, 3, -30, 13, 45]
The Sum Of Elements is 54
Is the stack empty? true

Program 4 : Use java.util.Stack.empty() method to implement error handling in program. 

For example, if you are reading data from a file into a stack, you can check if the stack is empty after reading the data to ensure that the file is not empty.

Java

// Java code to demonstrate error handling using empty() method

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
import java.util.Stack;

public class FileReadExample {

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

        // read data from file
        try {
            File file = new File("data.txt");
            Scanner scanner = new Scanner(file);
            while (scanner.hasNextLine()) {
                String line = scanner.nextLine();
                stack.push(line);
            }
            scanner.close();
        } catch (FileNotFoundException e) {
            System.out.println("File not found.");
        }

        // check if stack is empty
        if (stack.empty()) {
            System.out.println("File is empty.");
        } else {
            System.out.println("File is not empty. Stack contents:");
            while (!stack.empty()) {
                System.out.println(stack.pop());
            }
        }
    }

}

// This code is contributed by vishalkumarsahu04

Time Complexity: O(n), where n is the number of lines in the file.
Space Complexity : O(n), where n is the number of lines in the file.