Refactor hashcode() samples (#2377)

core-java/src/main/java/com/baeldung/hashcode/application/Application.java

@@ -1,24 +0,0 @@
-package com.baeldung.hashcode.application;
-
-import java.util.HashMap;
-import java.util.Map;
-
-import com.baeldung.hashcode.entities.User;
-
-public class Application {
-
-    public static void main(String[] args) {
-        Map<User, User> users = new HashMap<>();
-        User user1 = new User(1L, "John", "john@domain.com");
-        User user2 = new User(2L, "Jennifer", "jennifer@domain.com");
-        User user3 = new User(3L, "Mary", "mary@domain.com");
-
-        users.put(user1, user1);
-        users.put(user2, user2);
-        users.put(user3, user3);
-
-        if (users.containsKey(user1)) {
-            System.out.print("User found in the collection");
-        }
-    }
-}