class Animal {
    protected String name;

    public Animal(String name) {
        this.name = name;
    }

    @Override
    public boolean equals(Object obj) {
        if(obj == null) return false;
        if (???) {
            Animal other = (Animal) obj;
            return name.equals(other.name);
        }
        return false;
    }
}

class Dog extends Animal {
    public Dog(String name) {
        super(name);
    }
}
class Main {
    public static void main(String[] args) {
        Animal a = new Animal("Bobik");
        Dog d = new Dog("Bobik");
        System.out.println(a.equals(d));
    }
}

class Parent {
    static void hello() { System.out.println("Parent"); }
}
class Child extends Parent {
    static void hello() { System.out.println("Child"); }
}

public class Test {
    public static void main(String[] args) {
        Parent p = new Child();
        p.hello();
    }
}

public class Test {
    static void change(String s) {
        s = "new";
    }

    public static void main(String[] args) {
        String str = "old";
        change(str);
        System.out.println(str);
    }
}

public class ArrayTest {
    public static void main(String[] args) {
        int[] numbers = null;
        System.out.println(numbers.length);
    }
}

class A {}
class B extends A {}

class Test {
    A foo() { return new A(); }
    B foo() { return new B(); }
}