Question 1

Consider the following code snippet: Public static void fun(T[] t) { . . . } Erasure by the compiler of method fun will generate which result? A) public static void fun(Object[] t) { . . . } B) public static

Accepted Answer

The erasure process in generic programming replaces the type parameter of a generic class or a generic method with a concrete type. In this case, the type parameter T will be replaced by Object. Therefore, the erasure of the method fun will generate option C, public static void fun(Object[] t) { . . . }. This is because the array that is being passed as a parameter is an array of type T, which is replaced by Object during erasure. Option A is incorrect because the type parameter is not being erased completely; it is just being replaced with Object. Option B is incorrect because it is not specifying an array type. Option D is incorrect because it is not specifying an array type and it is not generic.

Question 2

Erasure of types limits Java code somewhat with generics. Which of the following are limitations of generic code?
I cannot instantiate a type variable
II cannot return a type variable
III cannot pass a type variable
A) I
B) II
C) III
D) II and III

Accepted Answer

The answer of Erasure of types limits Java code somewhat...

Question 3

Generics limit Java code somewhat. Which of the following are limitations of generic code?
I cannot declare static variables of a generic type
II cannot declare static methods of a generic type
III cannot declare static inner classes of a generic type
A) I
B) II
C) I and II
D) I, II, and III

Accepted Answer

All of the statements are limitations of generic code in Java. Static variables, methods and inner classes cannot be declared using a generic type.

Question 4

Consider the following code snippet: Public class LinkedList { Private E defaultValue; Public static List replicate(E value, int n) { . . . } Private class Node { public String data; public Node next;) ) . . } What is wrong with this code? A) Cannot declare the variable defaultValue as a generic type. B) Cannot pass a generic type as an argument to a method. C) Cannot have a static method in a generic class as shown. D) Cannot have an inner class in a generic class.

Accepted Answer

It is not possible to have a static method with a generic type parameter in a generic class. The reason is that the actual type parameter is not known until an instance of the generic class is created. However, static methods belong to the class itself and do not depend on any specific instance, so they cannot access the type parameter.

Question 5

Consider the following code snippet: Public static E min(E[] objects) Which of the following represents the result of type erasure on this code? A) public static Measurable E min(Measurable E[] objects) B) public static Measurable min(Measurable[] objects) C) public static E min(Measurable E[] objects) D) This code is illegal and type erasure will not occur.

Accepted Answer

Type erasure removes the type parameter and replaces it with its first bound or Object if there is no bound. In this case, the type parameter E has a bound of Measurable. So, after type erasure, the code will become:

public static Measurable min(Measurable[] objects)

Question 6

Which of the following necessitates the type erasure process?
I The Java virtual machine does not work with generic types
II To maintain backward compatibility to older versions of Java
III Generics do not work with primitives
A) I
B) II
C) I and II
D) I and III

Accepted Answer

Type erasure is necessary in Java to maintain backward compatibility with older versions of Java and because the Java virtual machine (JVM) does not work with generic types. Additionally, generics do not work with primitives, so type erasure is necessary to handle these cases as well. Therefore, both options I and II are correct, and the correct answer is C.

Question 7

What is the result when a program constructs a generic class without passing a type variable, as in the following code?
Stack stack = new Stack();
I the program will compile and run
II the compiler will issue an error
III the compiler will issue a warning
A) I
B) II
C) III
D) I and III

Accepted Answer

The answer of What is the result when a program...

Question 8

Given the following declaration, what is the type parameter in Stack replaced with? Private Stack myStack = new Stack(); A) String B) Object C) int D) Stack

Accepted Answer

The type parameter in Stack<E> is replaced by the specific type String in the declaration. Therefore, the answer is A.

Question 9

To maintain compatibility with pre-generic Java, type parameters are replaced by ordinary types called ____.
A) primitives
B) raw types
C) Object
D) generics

Accepted Answer

Type parameters are replaced by raw types in order to maintain compatibility with pre-generic Java. Raw types are ordinary types that do not have any type parameters specified. This allows code written before the introduction of generics to use the generic syntax without requiring changes to the code. Option A is incorrect as primitives are not used in place of type parameters. Option C is incorrect as Object is a specific type and not a replacement for type parameters. Option D is incorrect as generics are the actual type parameters being replaced in order to maintain compatibility with pre-generic Java.

Question 10

Consider the following code snippet:
Public class LinkedList<E>
{
Private E defaultValue; //Line 1
Public void add(E value, int n) { . . . } //Line 2
Private static class Node { public E data; public Node next;)//Line 3
) . .
}
What is wrong with this code?
A) Cannot declare the variable defaultValue as a generic type.
B) Cannot pass a generic type as an argument to a method.
C) Cannot have a static method in a generic class as shown.
D) Cannot have a static inner class in a generic class as shown.

Accepted Answer

The answer of Consider the following code snippet:
Public class LinkedList<E>
{
Private...

Question 11

Given the following declaration, what is the type parameter in Stack<E> replaced with?
Private Stack myStack = new Stack();
A) String
B) Object
C) int
D) it is a compiler error

Accepted Answer

Since no type is specified for the Stack object, it defaults to type Object. Therefore, the type parameter in Stack<E> is replaced with Object.

Question 12

Suppose a generic method accepts a generic unconstrained argument p. What restrictions are placed on p by the compiler?
A) Can only execute Object class methods.
B) Can only execute methods from its own class.
C) Can not execute any methods.
D) There are no restrictions.

Accepted Answer

The answer of Suppose a generic method accepts a generic...

Question 13

If a class requires two generic type variables, how many can you legally provide in Java?
I 0
II 1
III 2
A) I
B) II
C) I and II
D) I and III

Accepted Answer

The answer of If a class requires two generic type...

Question 14

Consider the following code snippet: Public interface MyInterface { . . . } Public interface YourInterface extends MyInterface { . . . } Which of these are legal class declarations? I public class SomeClass implements YourInterface { . . . } II public class SomeClass implements YourInterface { . . . } III public class SomeClass implements YourInterface { . . . } A) I B) III C) I and II D) I and III

Accepted Answer

The answer of Consider the following code snippet:
Public interface MyInterface<E>...

Question 15

Generics limit Java code somewhat. Which of the following are considered limitations of generic code?
I cannot have an array of a generic type
II cannot have primitive type variables
III cannot construct an object of a generic type
A) I
B) II
C) III
D) I, II and III

Accepted Answer

I - Arrays in Java are covariant. This means that an array of a supertype can hold elements of that supertype or any of its subtypes, but this is not the case with generic types as the type information is erased at runtime. Therefore, we cannot have an array of a generic type, only an array of Object. II - Primitive types are not considered to be objects in Java. Since generics require that the type be specified as an object, we cannot use primitive types as generic type parameters. III - We can construct an object of a generic type using the constructor of the class that implements the generic type. For example: `List myList = new ArrayList();`

Question 16

Which of the following are restrictions of Java generic programming?
I You cannot use the assignment operator = to assign one generic object to another.
II You cannot use the == operator to compare two generic objects.
III You cannot construct arrays of generic types.
A) I
B) II
C) III
D) I and III

Accepted Answer

The answer of Which of the following are restrictions of...

Question 17

Which of the following statements about the Java virtual machine is correct?
A) The Java virtual machine always replaces type parameters with their upper bounds.
B) The Java virtual machine always replaces type parameters with their lower bounds.
C) The Java virtual machine always replaces type parameters with type Object.
D) The Java virtual machine replaces type parameters with their bounds or with type Object.

Accepted Answer

The Java virtual machine replaces type parameters with their bounds or with type Object, depending on the context. If a type parameter is used in a way that necessitates a specific type, such as in a method call, it will be replaced with its bound. If it is used in a way that doesn't depend on a specific type, such as in a generic class declaration, it will be replaced with type Object.

Question 18

Consider the following code snippet:
Public class LinkedList<E>
{
Private static E defaultValue; //Line 1
Public void add(E value, int n) { . . . } //Line 2
Private class Node { public String data; public Node next;)//Line 3
) . .
}
What is wrong with this code?
A) Cannot declare the variable defaultValue as static.
B) Cannot pass a generic type as an argument to a method as shown.
C) Cannot have an inner class in a generic class as shown.
D) Cannot declare the variable defaultValue as a generic data type.

Accepted Answer

A non-static type variable cannot be declared as static. Therefore, line 1 is invalid.

Quiz 18: Generic Classes

Consider the following code snippet: Public static <T> void fun(T[] t) { . . . } Erasure by the compiler of method fun will generate which result?

Erasure of types limits Java code somewhat with generics. Which of the following are limitations of generic code? I cannot instantiate a type variable II cannot return a type variable III cannot pass a type variable

Generics limit Java code somewhat. Which of the following are limitations of generic code? I cannot declare static variables of a generic type II cannot declare static methods of a generic type III cannot declare static inner classes of a generic type

Consider the following code snippet: Public class LinkedList<E> { Private E defaultValue; Public static List<E> replicate(E value, int n) { . . . } Private class Node { public String data; public Node next;) ) . . } What is wrong with this code?

Consider the following code snippet: Public static <E extends Measurable> E min(E[] objects) Which of the following represents the result of type erasure on this code?

Which of the following necessitates the type erasure process? I The Java virtual machine does not work with generic types II To maintain backward compatibility to older versions of Java III Generics do not work with primitives

What is the result when a program constructs a generic class without passing a type variable, as in the following code? Stack stack = new Stack() ; I the program will compile and run II the compiler will issue an error III the compiler will issue a warning

Given the following declaration, what is the type parameter in Stack<E> replaced with? Private Stack<String> myStack = new Stack<String>() ;

To maintain compatibility with pre-generic Java, type parameters are replaced by ordinary types called ____.

Consider the following code snippet: Public class LinkedList<E> { Private E defaultValue; //Line 1 Public void add(E value, int n) { . . . } //Line 2 Private static class Node { public E data; public Node next;) //Line 3 ) . . } What is wrong with this code?

Given the following declaration, what is the type parameter in Stack<E> replaced with? Private Stack myStack = new Stack() ;

Suppose a generic method accepts a generic unconstrained argument p. What restrictions are placed on p by the compiler?

If a class requires two generic type variables, how many can you legally provide in Java? I 0 II 1 III 2

Generics limit Java code somewhat. Which of the following are considered limitations of generic code? I cannot have an array of a generic type II cannot have primitive type variables III cannot construct an object of a generic type

Which of the following are restrictions of Java generic programming? I You cannot use the assignment operator = to assign one generic object to another. II You cannot use the == operator to compare two generic objects. III You cannot construct arrays of generic types.

Which of the following statements about the Java virtual machine is correct?

Consider the following code snippet: Public class LinkedList<E> { Private static E defaultValue; //Line 1 Public void add(E value, int n) { . . . } //Line 2 Private class Node { public String data; public Node next;) //Line 3 ) . . } What is wrong with this code?