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Java Program to Reverse a String Using Stacks
In this article, we will understand how to reverse a string using stacks. String is a datatype that contains one or more characters and is enclosed in double quotes(“ ”). The stack is a linear data structure that is used to store the collection of objects. It is based on Last-In-First-Out (LIFO).
Below is a demonstration of the same −
Suppose our input is −
Input string: Java Program
The desired output would be −
Reversed string: margorP avaJ
Algorithm
Step 1 - START Step 2 - Declare two string values namely input_string and result, a stack value namely stack, and a char value namely reverse. Step 3 - Define the values. Step 4 - Iterate over each characters of the string using a for-loop and push each character to the stack using ‘push’ keyword. Step 5 - Now, pop each of the elements in the stack using ‘pop’ keyword and assign it to the result string. Step 6 - Display the result Step 7 - Stop
Example 1
Here, we bind all the operations together under the ‘main’ function.
import java.util.*;
public class ReverseString {
public static void main(String[] args) {
System.out.println("Required packages have been imported");
String input_string = "Java Program";
System.out.println("The string is defined as " +input_string);
char[] reverse = new char[input_string.length()];
Stack<Character> stack = new Stack<Character>();
for (int i = 0; i < input_string.length(); i++) {
stack.push(input_string.charAt(i));
}
int i = 0;
while (!stack.isEmpty()) {
reverse[i++] = stack.pop();
}
String result = new String(reverse);
System.out.println("\nThe reversed string is: " + result);
}
}Output
Required packages have been imported The string is defined as Java Program The reversed string is: margorP avaJ
Example 2
Here, we encapsulate the operations into functions exhibiting object oriented programming.
import java.util.*;
public class ReverseString {
public static String reverse_string(String input_string) {
char[] reverse = new char[input_string.length()];
Stack<Character> stack = new Stack<Character>();
for (int i = 0; i < input_string.length(); i++) {
stack.push(input_string.charAt(i));
}
int i = 0;
while (!stack.isEmpty()) {
reverse[i++] = stack.pop();
}
return new String(reverse);
}
public static void main(String[] args) {
System.out.println("Required packages have been imported");
String input_string = "Java Program";
System.out.println("The string is defined as " +input_string);
System.out.println("\nThe reversed string is: " + reverse_string(input_string));
}
}Output
Required packages have been imported The string is defined as Java Program The reversed string is: margorP avaJ
Updated on: 29-Mar-2022
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