fix: branch up-to-date merge error

Author: S-M-J-I

src/main/java/com/thealgorithms/stacks/GreatestElementConstantTime.java

@@ -12,8 +12,8 @@
  * Problem: https://www.baeldung.com/cs/stack-constant-time
  */
 public class GreatestElementConstantTime {
-    private Stack<Integer> mainStack;
-    private Stack<Integer> maxStack;
+    private Stack<Integer> mainStack; // initialize a mainStack
+    private Stack<Integer> maxStack; // initialize a maxStack
 
     /**
      * Constructs two empty stacks

src/main/java/com/thealgorithms/stacks/SmallestElementConstantTime.java

@@ -12,8 +12,8 @@
  * Problem: https://www.baeldung.com/cs/stack-constant-time
  */
 public class SmallestElementConstantTime {
-    private Stack<Integer> mainStack;
-    private Stack<Integer> minStack;
+    private Stack<Integer> mainStack; // initialize a mainStack
+    private Stack<Integer> minStack; // initialize a minStack
 
     /**
      * Constructs two empty stacks