OCP Java Class Design and OOP 3

Question 1

What is the output of the following code?
```java
class Parent {
  String greet() { return "Parent"; }
}
class Child extends Parent {
  String greet() { return "Child"; }
}
Parent p = new Child();
System.out.println(p.greet());
```

Accepted Answer

Child

Answer

Method overriding uses dynamic dispatch — at runtime the JVM calls Child's `greet()` because the actual object is a Child.

Question 2

Which statement about `static` methods and inheritance is correct?

Accepted Answer

Static methods are hidden, not overridden, and use static dispatch

Answer

Static methods are hidden (not overridden); the method called depends on the reference type, not the runtime type.

Question 3

What does the `instanceof` operator return when tested against `null`?

Accepted Answer

false

Answer

`null instanceof AnyType` always returns `false` — no exception is thrown.

Question 4

Which of the following is true about interface variables in Java?

Accepted Answer

They are implicitly public, static, and final

Answer

All fields declared in an interface are implicitly `public static final` — they are constants.

Question 5

In Java, what is the purpose of using `super()` as the first statement in a constructor?

Accepted Answer

To explicitly invoke a parent class constructor

Answer

`super()` calls a parent class constructor and must appear as the first statement in a subclass constructor.

(OCP) Oracle Certified Professional Practice Test

(OCP) Oracle Certified Professional Practice Test

OCP Java Class Design and OOP 3