Refactored ReverseStringUsingStack utility for reversing strings using stack

Author: navaneedan07

src/test/java/com/thealgorithms/strings/ReverseStringTest.java

@@ -5,6 +5,7 @@
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.util.stream.Stream;
+import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.Arguments;
 import org.junit.jupiter.params.provider.MethodSource;
@@ -41,7 +42,8 @@ public void testReverseString4(String input, String expectedOutput) {
     }
 
     @Test
-    public void testReverseString4WithNull() { Exception exception = assertThrows(IllegalArgumentException.class, () -> { ReverseString.reverse4(null); });
+    public void testReverseString4WithNull() {
+        Exception exception = assertThrows(IllegalArgumentException.class, () -> { ReverseString.reverse4(null); });
         String expectedMessage = "Input string cannot be null";
         String actualMessage = exception.getMessage();
         assertTrue(actualMessage.contains(expectedMessage));