checked the style and fixed it accordingly to set rules

src/main/java/core/basesyntax/HelloWorld.java

@@ -0,0 +1,47 @@
+package core.basesyntax;
+
+import core.basesyntax.model.Cat;
+import core.basesyntax.model.Dog;
+import java.time.LocalDate;
+
+public class HelloWorld {
+    private String str;
+    private int variable;
+    private int age;
+    private int size;
+
+    public static void main(String[] args) {
+        Dog dog = new Dog();
+        Cat cat = new Cat();
+    }
+
+    private String getFromOneToTen() {
+        String result = "";
+
+        for (int i = 0; i < 10; i++) {
+            if (i % 2 == 0) {
+                result = result + i + " ";
+            }
+        }
+        return result;
+    }
+
+    private void sayHello(String hello) {
+        System.out.println("Hello, Mate! I am happy to see you! This class looks weird!");
+        System.out.println("Your task is to fix the checkstyle in this file.");
+        System.out.println("Your goal is:");
+        System.out.println("To run `mvn clean package` and receive `BUILD SUCCESS` message");
+        System.out.println(hello);
+    }
+
+    private void initializeVariables() {
+        str = "Hello mates!";
+        System.out.println(str);
+        variable = LocalDate.now().getYear();
+        System.out.println("It is " + variable + "year");
+        age = 25;
+        System.out.println("I'm " + age);
+        size = 42;
+        System.out.println("The size is " + size);
+    }
+}

src/main/java/core/basesyntax/model/Cat.java

@@ -0,0 +1,16 @@
+package core.basesyntax.model;
+
+public class Cat {
+    private int age;
+    private String name;
+    private String ownerName;
+
+    @Override
+    public String toString() {
+        return "Cat{"
+                + "age=" + age
+                + ", name='" + name + '\''
+                + ", ownerName='" + ownerName + '\''
+                + '}';
+    }
+}

src/main/java/core/basesyntax/model/Dog.java

@@ -0,0 +1,4 @@
+package core.basesyntax.model;
+
+public class Dog {
+}