Oracle Java Certification Practice Test

1. Which keyword is used to prevent a class from being subclassed in Java?

Private

Final

Static

Abstract

2. What is the default value of an instance variable of type int in Java?

0

Null

Undefined

-1

3. Which interface must be implemented to create a custom comparator for sorting objects?

Iterable

Comparable

Comparator

Serializable

4. In a try-catch-finally block, when is the finally block executed?

Only if an exception occurs

Only if no exception occurs

Always, regardless of exception

Never, it is optional

5. Which collection class maintains insertion order and allows duplicate elements?

HashSet

TreeSet

ArrayList

HashMap

6. What does the synchronized keyword do in Java?

Increases code execution speed

Ensures thread-safe access to shared resources

Prevents memory leaks

Allows multiple inheritance

7. Which Stream operation is used to filter elements based on a condition?

Map()

Filter()

Reduce()

Collect()

8. What is the purpose of the @Override annotation in Java?

To mark a method as final

To indicate a method overrides a superclass method

To prevent method overloading

To make a method static

9. Which of the following is NOT a valid access modifier in Java?

Public

Private

Protected

Internal

10. What does the 'instanceof' operator do?

Creates a new object instance

Checks if an object is an instance of a class

Compares object equality

Casts an object to a different type

Submit

13. What is the superclass of all classes in Java?

Parent

Base

Object

Class

Submit

15. Which method is called when an object is created in Java?

Init()

Create()

Constructor

New()