feat: add ReverseStringUsingStack (#6451)

src/main/java/com/thealgorithms/strings/ReverseStringUsingStack.java

@@ -0,0 +1,38 @@
+package com.thealgorithms.strings;
+
+import java.util.Stack;
+
+/**
+ * A utility class to reverse a given string using a Stack.
+ */
+public final class ReverseStringUsingStack {
+
+    // Private constructor to prevent instantiation of utility class
+    private ReverseStringUsingStack() {
+        throw new UnsupportedOperationException("Utility class");
+    }
+
+    /**
+     * Reverses the input string using a Stack.
+     *
+     * @param str the input string to be reversed
+     * @return the reversed string
+     */
+    public static String reverse(String str) {
+        StringBuilder sb = new StringBuilder();
+        Stack<Character> stack = new Stack<>();
+
+        // Push each character of the string into the stack
+        for (int i = 0; i < str.length(); ++i) {
+            stack.push(str.charAt(i));
+        }
+
+        // Pop each character from the stack and append to StringBuilder
+        while (!stack.isEmpty()) {
+            sb.append(stack.pop());
+        }
+
+        // Return the reversed string
+        return sb.toString();
+    }
+}