class C {
	int a;
	static int b;
	
	void main(/* C this */) {
	}
	
	static void f() {
		// fully qualified form
		System.out.println(this.a);	// BAD
		System.out.println(a);		// BAD

		System.out.println(C.b);	// OK
		System.out.println(b);		// OK
	}

}



class Animal { int age; }
class Human extends Animal { String name; }
class Student extends Human { int id; }


Human human = new Human();
Student student = new Student();
Human human = new Student();
Object obj = human;
Object obj = new Student();

Human human = new Random().nextBoolean() ? new Student() : new Human();
System.out.println(human.name);	// OK
System.out.println(human.id);	// wrong

// wrong
Student student = new Random().nextBoolean() ? new Student() : new Human();


class A extends B, C {}    // not Java