Java.lang Class - General Questions

Which class is the root of the Java class hierarchy?

What is the output of the following program?

public class Main {
    public static void main(String[] args) {
        System.out.println(Math.max(3, 9) + Math.min(3, 9));
    }
}

What is the output of the following program?

public class Main {
    public static void main(String[] args) {
        System.out.println(Math.ceil(4.1) + " " + Math.floor(4.9));
    }
}

What is the output of the following program?

public class Main {
    public static void main(String[] args) {
        Object o = "text";
        System.out.println(o instanceof String s ? s.length() : -1);
    }
}

What is the output of the following program?

public class Main {
    public static void main(String[] args) {
        System.out.println(Math.abs(-7.5));
    }
}