SCJP Java Generics, Enums, and Autoboxing

Question 1

What is the primary benefit of using generics in Java?

Accepted Answer

Type safety at compile time, eliminating the need for explicit casting

Answer

Improved runtime performance

Answer

Allowing methods to return multiple types

Answer

Enabling dynamic typing

Question 2

What is type erasure in Java generics?

Accepted Answer

Removing type parameter information at compile time so the bytecode uses raw types

Answer

The process of deleting generic classes at compile time

Answer

Converting generic types to Object at runtime only

Answer

A compiler optimization for generics

Question 3

What does autoboxing in Java do?

Accepted Answer

Automatically converts primitive types to their wrapper class equivalents

Answer

Converts arrays to ArrayLists automatically

Answer

Boxes multiple return values into a tuple

Answer

Wraps exceptions in RuntimeException

Question 4

Which of the following correctly declares a generic method in Java?

Accepted Answer

public <T> T swap(T a, T b)

Answer

public T swap(T a, T b)

Answer

public Generic<T> swap(T a, T b)

Answer

public static T swap(T a, T b)

Question 5

What is an enum in Java?

Accepted Answer

A special class that represents a group of named constants

Answer

An interface with constants

Answer

A collection of primitive values

Answer

A type of annotation

Question 6

What is the result of unboxing a null Integer in Java?

Accepted Answer

Throws NullPointerException

Answer

Returns 0

Answer

Throws IllegalArgumentException

Answer

Returns Integer.MIN_VALUE