BAEL-4953: Fix FindBugs annotations (#10772)

Co-authored-by: Krzysztof Woyke <krzysztof.woyke.sp@lhsystems.com>

patterns/design-patterns-behavioral/src/main/java/com/baeldung/nulls/FindBugsAnnotations.java

@@ -1,12 +1,12 @@
 package com.baeldung.nulls;
 
-import org.jetbrains.annotations.NotNull;
-import org.jetbrains.annotations.Nullable;
 
+import edu.umd.cs.findbugs.annotations.NonNull;
+import edu.umd.cs.findbugs.annotations.Nullable;
 
 public class FindBugsAnnotations {
 
-    public void accept(@NotNull Object param) {
+    public void accept(@NonNull Object param) {
         System.out.println(param.toString());
     }
 
@@ -14,7 +14,7 @@ public class FindBugsAnnotations {
         System.out.println("Printing " + param);
     }
 
-    @NotNull
+    @NonNull
     public Object process() throws Exception {
         Object result = doSomething();
         if (result == null) {