Master Generic Programming in Object-Oriented Programming

Question 1

What is the primary purpose of type parameters in generic classes?

Accepted Answer

To specify the data type(s) that the class can operate on

Answer

To restrict the type of objects that can be passed to the class

Answer

To improve the performance of the class

Answer

To make the class more readable

Question 2

What is the key difference between a generic class and a non-generic class?

Accepted Answer

Generic classes can operate on multiple data types, while non-generic classes are limited to a single data type.

Answer

Non-generic classes can operate on multiple data types, while generic classes are limited to a single data type.

Answer

Generic classes are more efficient than non-generic classes.

Answer

Non-generic classes are more efficient than generic classes.

Question 3

What is the difference between a wildcard and a type parameter?

Accepted Answer

Wildcards can represent any type, while type parameters must be specified.

Answer

Type parameters can represent any type, while wildcards must be specified.

Answer

Wildcards are more efficient than type parameters.

Answer

Type parameters are more efficient than wildcards.

Question 4

Which of the following is a primary advantage of using generics in Java?

Accepted Answer

Enhanced code reusability and flexibility

Answer

Improved type checking and safety

Answer

Simplified syntax and reduced code complexity

Answer

Faster program execution and reduced memory usage

Question 5

Which of the following is a potential drawback of using generics?

Accepted Answer

Increased code complexity due to the introduction of additional type parameters

Answer

Reduced code readability

Question 6

What is the purpose of the erasure process in Java generics?

Accepted Answer

To remove type information from generic code during compilation, leaving only the underlying non-generic code

Answer

The process of adding type information to generic code at runtime

Question 7

What is the correct syntax for defining a generic class in Java?

Accepted Answer

public class MyClass<T> {}

Answer

public class MyClass {}

Answer

public class MyClass { T value; }

Answer

public class MyClass { <T> T value; }

Question 8

What is the purpose of the wildcard character '?' in generic types?

Accepted Answer

To represent any type

Answer

To represent unknown types

Answer

To represent multiple types simultaneously

Answer

To restrict type parameters to specific types

Question 9

Identify the valid example of generic code:

Accepted Answer

public class MyClass<T> { public T value; }

Answer

public class MyClass {}

Answer

public class MyClass { <T> T value; }

Answer

public class MyClass extends T {}

Question 10

What is the fundamental difference between a generic class and a raw type?

Accepted Answer

Generic classes employ type parameters, while raw types do not

Answer

Raw types offer better efficiency compared to generic classes

Answer

Generic classes can only be instantiated with specific data types, whereas raw types can accept any data type

Answer

There is no distinction between generic classes and raw types

Question 11

Which of the following is an invalid type argument for a generic class?

Accepted Answer

float

Answer

Integer

Answer

String

Answer

List<Integer>

Question 12

What is the function of the 'extends' keyword in a generic type bound?

Accepted Answer

To specify that the type parameter must be a subtype of the specified type

Answer

To specify that the type parameter must be a supertype of the specified type

Answer

To specify that the type parameter must be identical to the specified type

Answer

To specify that the type parameter must not be the specified type

Question 13

What is the intended purpose of bounded wildcards?

Accepted Answer

To specify that a type parameter must be a subtype or supertype of a specified type

Answer

To specify that a type parameter cannot be a subtype or supertype of a specified type

Answer

To specify that a type parameter must be identical to a specified type

Answer

To specify that a type parameter cannot be identical to a specified type

Question 14

Which of the following syntax is correct to declare a generic class that accepts any type in Java?

Accepted Answer

class MyClass<T> {}

Answer

class MyClass MyClass {}

Answer

class MyClass<T> MyClass(T t) {}

Answer

class MyClass<T>() {}

Question 15

What is a key benefit of using a generic method?

Accepted Answer

It enables methods to operate on various data types.

Answer

It eliminates the need for method overloading.

Answer

It improves code readability.

Answer

It enhances program performance.

Question 16

What is the correct syntax to declare a generic class in Java?

Accepted Answer

public class <T>

Answer

public class <type> T

Answer

public class T<type>

Answer

public class T

Question 17

Which of the following is NOT an advantage of utilizing generics?

Accepted Answer

Reduced code performance

Answer

Increased code reusability

Answer

Enhanced type safety

Answer

Improved code readability

Question 18

What is the primary purpose of bounded types in generics?

Accepted Answer

To restrict the types of data that can be stored in a generic class or method

Answer

To increase the flexibility of generic classes and methods

Answer

To improve the efficiency of generic code

Answer

To enhance the portability of generic code

Question 19

Which of the following represents a valid example of a generic method?

Accepted Answer

public <T> void printArray(T[] array)

Answer

public void printArray(T[] array)

Answer

public <type> printArray(type[] array)

Answer

public void printArray<T>(T[] array)

Question 20

What is the distinction between a raw type and a parameterized type in generics?

Accepted Answer

Raw type: lacks type parameters, Parameterized type: specifies type parameters

Answer

Raw type: compatible with any type, Parameterized type: incompatible with any type

Answer

Raw type: more efficient, Parameterized type: less efficient

Answer

Raw type: more flexible, Parameterized type: less flexible

Question 21

What purpose does type erasure serve in generics?

Accepted Answer

Type erasure removes type information during runtime, enhancing flexibility

Answer

Type erasure adds type information during runtime, ensuring type safety

Answer

Type erasure is not utilized in generics

Answer

Type erasure prevents generics from being used with primitive data types

Question 22

What is the purpose of the `<T>` notation in a generic class declaration?

Accepted Answer

To indicate that the class is generic

Answer

To specify the data type of the class

Answer

To create a template for the class

Answer

To restrict access to the class

Question 23

What is the difference between a generic class and a generic method?

Accepted Answer

A generic class defines a template for creating objects of different data types, while a generic method defines a template for performing an operation on different data types.

Answer

A generic class can operate on different data types, while a generic method can only operate on a specific data type.

Answer

There is no difference between a generic class and a generic method.

Answer

A generic method can be declared within a generic class, but a generic class cannot be declared within a generic method.

Question 24

What is the difference between bounded and unbounded generics?

Accepted Answer

Bounded generics restrict the data types that can be used with a generic class or method, while unbounded generics do not.

Answer

Bounded generics are more efficient than unbounded generics.

Answer

Unbounded generics are more flexible than bounded generics.

Answer

There is no difference between bounded and unbounded generics.

Question 25

What is the purpose of the `? super T` wildcard in Java generics?

Accepted Answer

To represent a wildcard type that can be any superclass of T

Answer

To represent a wildcard type that can be any subclass of T

Answer

To represent a wildcard type that can be any type

Answer

To represent a wildcard type that cannot be any type

Question 26

Which of the following is a valid example of a generic class?

Accepted Answer

class Box<T> { ... }

Answer

class Box { ... }

Question 27

Which of the following is a limitation of using generics?

Accepted Answer

Generics can introduce runtime errors

Question 28

Which of the following is an example of a type bound in generics?

Accepted Answer

class Box<T extends Number> { ... }

Answer

class Box<T> { ... }

Question 29

Which of the following is a valid declaration for a generic class?

Accepted Answer

class MyList<T extends Number> {}

Answer

class MyList<T super Number> {}

Answer

class MyList<T where T : Number> {}

Answer

class MyList<T extends List> {}

Question 30

Which syntax correctly defines a generic class named 'Container' that can process any data type?

Accepted Answer

public class Container<T> { ... }

Answer

public class Container { ... }<T>

Answer

public class Container[T] { ... }

Answer

public class { ... }<T> Container

Question 31

What is the purpose of the 'extends' keyword in generic class declarations?

Accepted Answer

To specify the upper bound of the type parameter

Answer

To specify the lower bound of the type parameter

Answer

To specify the equality constraint for the type parameter

Answer

To specify the nullability of the type parameter

Question 32

What is the primary purpose of using bounded wildcards in generics?

Accepted Answer

To specify a range of acceptable types for the type parameter

Answer

To allow any type to be used as the type parameter

Answer

To prevent the use of primitive data types as type parameters

Answer

To specify the nullability of the type parameter

Question 33

Which of the following is the correct syntax to declare a generic class in Java?

Accepted Answer

public class MyGenericClass<T> {}

Answer

public class MyGenericClass {}

Answer

public class<T> MyGenericClass {}

Answer

public class<T> MyGenericClass

Question 34

What is the purpose of the wildcard character (<>) in generics?

Accepted Answer

To represent any type

Answer

To represent a specific type

Answer

To restrict the type of a generic parameter

Answer

To indicate that a generic parameter is optional

Question 35

What does the following code snippet do?

Accepted Answer

Creates a generic method that prints the elements of an array

Answer

Creates a generic class that stores an array of elements

Answer

Creates a generic interface that defines a method for printing arrays

Answer

Creates a generic annotation that can be applied to arrays

Question 36

What is the key difference between covariant and contravariant generics?

Accepted Answer

Covariant generics allow subtyping for type parameters, while contravariant generics do not.

Answer

Contravariant generics allow subtyping for type parameters, while covariant generics do not.

Answer

Covariant generics allow you to specify upper bounds for type parameters, while contravariant generics do not.

Answer

Contravariant generics allow you to specify upper bounds for type parameters, while covariant generics do not.

Question 37

What is the purpose of the extends keyword when used in generics?

Accepted Answer

To specify an upper bound for a type parameter

Answer

To specify a lower bound for a type parameter

Answer

To indicate that a generic class inherits from another generic class

Answer

To indicate that a generic class implements an interface

Question 38

Which of the following is a correct way to declare a generic class?

Accepted Answer

class MyGenericClass<T> {...}

Answer

class MyGenericClass implements T {...}

Answer

class MyGenericClass(T) {...}

Answer

class MyGenericClass extends T {...}

Question 39

In generics, what is the distinction between covariance and contravariance?

Accepted Answer

Covariance permits a generic type to be utilized as a subtype, whereas contravariance allows it to be used as a supertype.

Answer

Covariance enables a generic type to be utilized as a supertype, whereas contravariance allows it to be used as a subtype.

Answer

Covariance and contravariance are equivalent ideas.

Answer

Covariance and contravariance are unrelated to generics.

Question 40

Which technique is used to instantiate a generic class?

Accepted Answer

new()

Answer

create()

Answer

instance()

Answer

factory()

Question 41

What is the main purpose of using wildcard generics?

Accepted Answer

To denote types that can be any subtype of a specified type

Answer

To denote types that can be any supertype of a specified type

Answer

To denote types that can be any unrelated type

Answer

To denote types that cannot be specified

Question 42

Explain the difference between type erasure and generic type information.

Accepted Answer

Type erasure removes all generic type information at compile time, while generic type information is preserved at runtime.

Answer

Generic type information is removed at compile time, while type erasure preserves it at runtime.

Answer

Type erasure and generic type information are synonymous terms.

Answer

Neither type erasure nor generic type information are used in Java

Question 43

Provide an example of a generic interface in Java.

Accepted Answer

java.util.List

Answer

java.lang.String

Answer

java.math.BigInteger

Answer

java.io.File