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(); }
}

System.out.println(0.1 + 0.2 == 0.3); // false 😅

Math.abs(a - b) < 1e-9

System.out.println(Double.compare(0.1 + 0.2, 0.3) == 0); // false

public class Main {
    public static void main(String[] args) {
        double a = 0.0;
        double b = -0.0;

        System.out.println(a == b);
        System.out.println(1 / a == 1 / b);
    }
}