fix: add generic type parameters to resolve compilation warnings

Author: gowtham1412-p

src/test/java/com/thealgorithms/datastructures/stacks/StackUsingLinkedListTest.java

@@ -8,96 +8,83 @@
 import org.junit.jupiter.api.Test;
 
 class StackUsingLinkedListTest {
-
     @Test
     void testPushAndPop() {
-        StackUsingLinkedList stack = new StackUsingLinkedList();
+        StackUsingLinkedList<Integer> stack = new StackUsingLinkedList<>();
         stack.push(10);
         stack.push(20);
         stack.push(30);
-
         assertEquals(30, stack.pop());
         assertEquals(20, stack.pop());
         assertEquals(10, stack.pop());
     }
 
     @Test
     void testPeek() {
-        StackUsingLinkedList stack = new StackUsingLinkedList();
+        StackUsingLinkedList<Integer> stack = new StackUsingLinkedList<>();
         stack.push(100);
         stack.push(200);
-
         assertEquals(200, stack.peek());
         assertEquals(200, stack.peek());
         assertEquals(2, stack.size());
     }
 
     @Test
     void testIsEmpty() {
-        StackUsingLinkedList stack = new StackUsingLinkedList();
+        StackUsingLinkedList<Integer> stack = new StackUsingLinkedList<>();
         assertTrue(stack.isEmpty());
-
         stack.push(5);
         assertFalse(stack.isEmpty());
-
         stack.pop();
         assertTrue(stack.isEmpty());
     }
 
     @Test
     void testSize() {
-        StackUsingLinkedList stack = new StackUsingLinkedList();
+        StackUsingLinkedList<Integer> stack = new StackUsingLinkedList<>();
         assertEquals(0, stack.size());
-
         stack.push(1);
         assertEquals(1, stack.size());
-
         stack.push(2);
         stack.push(3);
         assertEquals(3, stack.size());
-
         stack.pop();
         assertEquals(2, stack.size());
     }
 
     @Test
     void testPopEmptyStack() {
-        StackUsingLinkedList stack = new StackUsingLinkedList();
+        StackUsingLinkedList<Integer> stack = new StackUsingLinkedList<>();
         assertThrows(RuntimeException.class, stack::pop);
     }
 
     @Test
     void testPeekEmptyStack() {
-        StackUsingLinkedList stack = new StackUsingLinkedList();
+        StackUsingLinkedList<Integer> stack = new StackUsingLinkedList<>();
         assertThrows(RuntimeException.class, stack::peek);
     }
 
     @Test
     void testMultipleOperations() {
-        StackUsingLinkedList stack = new StackUsingLinkedList();
-
+        StackUsingLinkedList<Integer> stack = new StackUsingLinkedList<>();
         assertTrue(stack.isEmpty());
-
         stack.push(1);
         stack.push(2);
         assertEquals(2, stack.pop());
-
         stack.push(3);
         stack.push(4);
         assertEquals(4, stack.peek());
         assertEquals(3, stack.size());
-
         assertFalse(stack.isEmpty());
     }
 
     @Test
     void testSingleElement() {
-        StackUsingLinkedList stack = new StackUsingLinkedList();
+        StackUsingLinkedList<Integer> stack = new StackUsingLinkedList<>();
         stack.push(42);
-
         assertEquals(42, stack.peek());
         assertEquals(1, stack.size());
         assertEquals(42, stack.pop());
         assertTrue(stack.isEmpty());
     }
-}
+}