Stack empty() Method in Java
Last Updated : 24 May, 2023
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()); } } OutputThe 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()); } } OutputThe 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 } OutputThe 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.