CSCI 2351: Object-Oriented Design - Ch. 11, 12, 13 Quizzes

parent class; general class

possible answers:

superclass

this

super

subclass

inheritance

extends

override

superclass

used to reference the calling object followed by the data field

possible answers:

superclass

this

super

subclass

inheritance

extends

override

this

used to invoke the superclass's methods and constructors

possible answers:

superclass

this

super

subclass

inheritance

extends

override

super

specialized class, child class; inherits accessible data fields and methods from its parent class and may also add new data fields and methods

possible answers:

superclass

this

super

subclass

inheritance

extends

override

subclass

enables you to define a general class (i.e., a superclass) and later extend it to more specialized classes (i.e., subclasses)

possible answers:

superclass

this

super

subclass

inheritance

extends

override

inheritance

keyword used to tell the compiler that a subclass belongs to a superclass

possible answers:

superclass

this

super

subclass

inheritance

extends

override

extends

a subclass modifies the implementation of a method defined in the superclass; must have the same signature as its superclass

possible answers:

superclass

this

super

subclass

inheritance

extends

override

override

Object-oriented programming allows you to derive new classes from existing classes. This is called ___.

a. abstraction

b. encapsulation

c. generalization

d. inheritance

d. inheritance

Which of the following statements are true? Select all that apply.

a. A subclass is a subset of a superclass.

b. "class A extends B" means A is a subclass of B.

c. A subclass is usually extended to contain more functions and more detailed information than its superclass.

d. "class A extends B" means B is a subclass of A.

b. "class A extends B" means A is a subclass of B.

c. A subclass is usually extended to contain more functions and more detailed information than its superclass.

Which of the following statements are true? Select all that apply.

a. The keyword this is used in an accessor/mutator method on a private data field within its own class

b. Private data fields must be accessed/mutated through public accessors/mutators if defined in the superclass

c. The keyword this is used for all private data fields.

d. Private data fields in a superclass can be used directly in a subclass.

e. The keyword this is not used in an accessor/mutator method on a private data field belonging to its superclass

a. The keyword this is used in an accessor/mutator method on a private data field within its own class

b. Private data fields must be accessed/mutated through public accessors/mutators if defined in the superclass

e. The keyword this is not used in an accessor/mutator method on a private data field belonging to its superclass

Suppose you create a class Square to be a subclass of GeometricObject. Analyze the following code:

Class Square extends GeometricObject {

double length;

Square(double length) {

GeometricObject(length);

}

}

a. The program has a compile error because you attempted to invoke the GeometricObject class's constructor illegally.

b. The program compiles fine, but it has a runtime error because of invoking the Square class's constructor illegally.

c. The program compiles fine, but you cannot create an instance of Square because the constructor does not specify the length of the Square.

a. The program has a compile error because you attempted to invoke the GeometricObject class's constructor illegally.

Which of the statements regarding the super keyword is incorrect?

a. You can use super to invoke a super class method.

b. You can use super.super.p to invoke a method in superclass's parent class.

c. You can use super to invoke a super class constructor.

d. You cannot invoke a method in superclass's parent class.

b. You can use super.super.p to invoke a method in superclass's parent class.

Analyze the following code:

public class Test {

public static void main(String[] args) {

B b = new B();

b.m(5);

System.out.println("i is " + b.i);

}

}

class A { int i;

public void m(int i) {

this.i = i;

}

}

class B extends A {

public void m(String s) {

}

}

a. The program has a compile error, because b.m(5) cannot be invoked since the method m(int) is hidden in B.

b. The program has a compile error, because m is overridden with a different signature in B.

c. The method m is not overridden in B. B inherits the method m from A and defines an overloaded method m in B.

d. The program has a runtime error on b.i, because i is not accessible from b.

c. The method m is not overridden in B. B inherits the method m from A and defines an overloaded method m in B.

a variable of a supertype can refer to a subtype object

possible answers:

polymorphism

override

overload

polymorphism

to provide a new implementation for a method in the subclass; the method must be the defined in the subclass using the same signature and the same or compatible return type

possible answers:

polymorphism

override

overload

override

to define multiple methods with the same name but different signatures

possible answers:

polymorphism

override

overload

overload

Analyze the following code:

public class Test {

public static void main(String[] args) {

new B();

}

}

class A {

int i = 7;

public A() {

System.out.println("i from A is " + i);

}

public void setI(int i) {

this.i = 2 * i;

}

}

class B extends A {

public B() {

setI(20);

// System.out.println("i from B is " + i);

}

@Override

public void setI(int i) {

this.i = 3 * i;

}

}

a. The constructor of class A is not called.

b. The constructor of class A is called and it displays "i from A is 60".

c. The constructor of class A is called and it displays "i from A is 7".

d. The constructor of class A is called and it displays "i from A is 40".

c. The constructor of class A is called and it displays "i from A is 7".

Analyze the following code:

public class Test {

public static void main(String[] args) {

new B();

}

}

class A {

int i = 7;

public A() {

setI(20);

System.out.println("i from A is " + i);

}

public void setI(int i) {

this.i = 2 * i;

}

}

class B extends A {

public B() {

// System.out.println("i from B is " + i);

}

@Override

public void setI(int i) {

this.i = 3 * i;

}

}

a. The constructor of class A is called and it displays "i from A is 40".

b. The constructor of class A is not called.

c. The constructor of class A is called and it displays "i from A is 7".

d. The constructor of class A is called and it displays "i from A is 60".

d. The constructor of class A is called and it displays "i from A is 60".

Which of the following statements are true? Select all that apply.

a. It is a compile error if two methods differ only in return type in the same class.

b. Overloading a method is to provide more than one method with the same name but with different signatures to distinguish them.

c. A static method cannot be overridden. If a static method defined in the superclass is redefined in a subclass, the method defined in the superclass is hidden.

d. To override a method, the method must be defined in the subclass using the same signature and compatible return type as in its superclass.

e. A private method cannot be overridden. If a method defined in a subclass is private in its superclass, the two methods are completely unrelated.

a. It is a compile error if two methods differ only in return type in the same class.

b. Overloading a method is to provide more than one method with the same name but with different signatures to distinguish them.

c. A static method cannot be overridden. If a static method defined in the superclass is redefined in a subclass, the method defined in the superclass is hidden.

d. To override a method, the method must be defined in the subclass using the same signature and compatible return type as in its superclass.

e. A private method cannot be overridden. If a method defined in a subclass is private in its superclass, the two methods are completely unrelated.

Which of the following statements are true? Select all that apply.

a. A method in a subclass can overload a method in the superclass.

b. A method can be overloaded in the same class.

c. If a method overrides another method, these two methods must have the same signature.

d. A method can be overridden in the same class.

e. If a method overloads another method, these two methods must have the same signature.

a. A method in a subclass can overload a method in the superclass.

b. A method can be overloaded in the same class.

c. If a method overrides another method, these two methods must have the same signature.

You can assign ___ to a variable of Object[] type. Select all that apply.

a. new char[100]

b. new java.util.Date[100]

c. new int[100]

d. new double[100]

e. new String[100]

b. new java.util.Date[100]

e. new String[100]

Given two reference variables t1 and t2, if t1 == t2 is true, t1.equals(t2) must be ___.

a. true

b. false

a. true

Given two reference variables t1 and t2, if t1.equals(t2) is true, t1 == t2 ___.

a. may be true or false

b. is always true

c. is always false

a. may be true or false

What is the output of the following code:

public class Test {

public static void main(String[] args) {

Object o1 = new Object();

Object o2 = new Object();

System.out.print((o1 == o2) + " " + (o1.equals(o2)));

}

}

a. false true

b. true false

c. true true

d. false false

d. false false

What is the output of the following code:

public class Test {

public static void main(String[] args) {

String s1 = new String("Java");

String s2 = new String("Java");

System.out.print((s1 == s2) + " " + (s1.equals(s2)));

}

}

a. false true

b. true false

c. true true

d. false false

a. false true

You can create an ArrayList using ___.

a. ArrayList()

b. new ArrayList[100]

c. new ArrayList<>()

d. new ArrayList[]

c. new ArrayList<>()

Invoking ___ removes all elements in an ArrayList x.

a. x.empty()

b. x.clean()

c. x.clear()

d. x.delete()

e. x.remove()

c. x.clear()

Suppose ArrayList x contains two strings [Beijing, Singapore]. Which of the following methods will cause the list to become [Beijing, Chicago, Singapore]?

a. x.add("Chicago")

b. x.add(0, "Chicago")

c. x.add(2, "Chicago")

d. x.add(1, "Chicago")

d. x.add(1, "Chicago")

Suppose ArrayList x contains two strings [Beijing, Singapore]. Which of the following method will cause the list to become [Beijing]? Select all that apply.

a. x.remove(2)

b. x.remove(1)

c. x.remove(0)

d. x.remove("Singapore")

b. x.remove(1)

d. x.remove("Singapore")

Suppose ArrayList x contains two strings [Beijing, Singapore]. Which of the following method will cause runtime errors? Select all that apply.

a. x.size()

b. x.set(2, "New York");

c. x.get(1)

d. x.get(2)

e. x.remove(2)

b. x.set(2, "New York");

d. x.get(2)

e. x.remove(2)

Invoking ___ returns the first element in an ArrayList x.

a. x.first()

b. x.get(0)

c. x.get()

d. x.get(1)

b. x.get(0)

Invoking ___returns the number of the elements in an ArrayList x.

a. x.getLength(0)

b. x.length(1)

c. x.size()

d. x.getSize()

c. x.size()

Analyze the following code. Select all that apply.

ArrayList list = new ArrayList();

list.add("Beijing");

list.add("Tokyo");

list.add("Shanghai");

list.set(3, "Hong Kong");

a. If you replace the last line by list.add(4, "Hong Kong"), the code will compile and run fine.

b. If you replace the last line by list.add(3, "Hong Kong"), the code will compile and run fine.

c. The last line in the code causes a runtime error because there is no element at index 3 in the array list.

d. The last line in the code has a compile error because there is no element at index 3 in the array list.

b. If you replace the last line by list.add(3, "Hong Kong"), the code will compile and run fine.

c. The last line in the code causes a runtime error because there is no element at index 3 in the array list.

What is the output of the following code?

ArrayList list = new ArrayList();

String s1 = new String("Java");

String s2 = new String("Java");

list.add(s1);

list.add(s2);

System.out.println((list.get(0) == list.get(1)) + " " + (list.get(0)).equals(list.get(1)));

a. true false

b. true true

c. false true

d. false false

c. false true

The output from the following code is ___.

java.util.ArrayList list = new java.util.ArrayList();

list.add("New York");

java.util.ArrayList list1 = list;

list.add("Atlanta");

list1.add("Dallas");

System.out.println(list1);

a. [New York, Atlanta]

b. [New York]

c. [New York, Atlanta, Dallas]

d. [New York, Dallas]

c. [New York, Atlanta, Dallas]

Suppose an ArrayList list contains {"red", "green", "red", "green"}. What is the list after the following code?

list.remove("red");

a. {"green", "red", "green"}

b. {"green", "green"}

c. {"red", "green", "green"}

d. {"red", "green", "red", "green"}

a. {"green", "red", "green"}

Suppose an ArrayList list contains {"red", "red", "green"}. What is the list after the following code?

String element = "red";

for (int i = 0; i < list.size(); i++)

if (list.get(i).equals(element))

list.remove(element);

a. {"green"}

b. {"red", "green"}

c. {}

d. {"red", "red", "green"}

b. {"red", "green"}

Suppose an ArrayList list contains {"red", "red", "green"}. What is the list after the following code?

String element = "red";

for (int i = 0; i < list.size(); i++)

if (list.get(i).equals(element)) {

list.remove(element);

i--;

}

a. {"red", "green"}

b. {"green"}

c. {}

d. {"red", "red", "green"}

b. {"green"}

Suppose an ArrayList list contains {"red", "red", "green"}. What is the list after the following code?

String element = "red";

for (int i = list.size() - 1; i >= 0; i--)

if (list.get(i).equals(element))

list.remove(element);

a. {"red", "red", "green"}

b. {"green"}

c. {}

d. {"red", "green"}

b. {"green"}

Show the output of the following code:

String[] array = {"red", "green", "blue"};

ArrayList list = new ArrayList<>(Arrays.asList(array));

list.add(0, "red");

System.out.println(list);

a. ["red", "red", "green", "blue"]

b. ["red", "green", "blue", "red"]

c. ["red", "green", "blue"]

d. ["red", "green", "red", "blue"]

a. ["red", "red", "green", "blue"]

Analyze the following code:

Double[] array = {1, 2, 3};

ArrayList list = new ArrayList<>(Arrays.asList(array));

System.out.println(list);

a. The code has a compile error because an integer such as 1 is automatically converted into an Integer object, but the array element type is Double.

b. The code is correct and displays [1, 2, 3].

c. The code is correct and displays [1.0, 2.0, 3.0].

d. The code has a compile error because asList(array) requires that the array elements are objects.

a. The code has a compile error because an integer such as 1 is automatically converted into an Integer object, but the array element type is Double.

Analyze the following code:

double[] array = {1, 2, 3};

ArrayList list = new ArrayList<>(Arrays.asList(array));

System.out.println(list);

a. The code has a compile error because asList(array) requires that the array elements are objects.

b. The code is correct and displays [1, 2, 3].

c. The code has a compile error because an integer such as 1 is automatically converted into an Integer object, but the array element type is Double.

d. The code is correct and displays [1.0, 2.0, 3.0].

a. The code has a compile error because asList(array) requires that the array elements are objects.

Analyze the following code:

double[] c = {1, 2, 3};

System.out.println(javA.util.Collections.max(c));

a. The code is correct and displays 3.

b. The code has a compile error on Integer[] c = {1, 2, 3}.

c. The code has a compile error on Collections.max(c). c cannot be an array.

d. The code is correct and displays 3.0.

c. The code has a compile error on Collections.max(c). c cannot be an array.

thrown by the JVM. There is little that the programmer can do other than notify the user and terminate

possible answers:

system error

throw

try

runtime error

catch

exception

finally clause

system error

executes an exception

possible answers:

system error

throw

try

runtime error

catch

exception

finally clause

throw

contains the code that is executed normally

possible answers:

system error

throw

try

runtime error

catch

exception

finally clause

try

errors that cause a problem to terminate abnormally

possible answers:

system error

throw

try

runtime error

catch

exception

finally clause

runtime error

handles the exception

possible answers:

system error

throw

try

runtime error

catch

exception

finally clause

catch

an object that represents an error or a condition that prevents execution from proceeding normally

possible answers:

system error

throw

try

runtime error

catch

exception

finally clause

exception

always executed regardless of whether an exception occurs or is caught

possible answers:

system error

throw

try

runtime error

catch

exception

finally clause

finally clause

Dividing an integer by zero, but not floating-point errors

possible answers:

ArithmeticException

IndexOutOfBoundsException

NullPointerException

VirtualMachineError

IllegalArgumentException

ClassNotFoundException

LinkageError

ArithmeticException

Index to an array is out of range

possible answers:

ArithmeticException

IndexOutOfBoundsException

NullPointerException

VirtualMachineError

IllegalArgumentException

ClassNotFoundException

LinkageError

IndexOutOfBoundsException

Attempt to access an object through a null reference variable

possible answers:

ArithmeticException

IndexOutOfBoundsException

NullPointerException

VirtualMachineError

IllegalArgumentException

ClassNotFoundException

LinkageError

NullPointerException

The JVM is broken or has run out of the resources it needs in order to continue operating

possible answers:

ArithmeticException

IndexOutOfBoundsException

NullPointerException

VirtualMachineError

IllegalArgumentException

ClassNotFoundException

LinkageError

VirtualMachineError

A method is passed an argument that is illegal or inappropriate

possible answers:

ArithmeticException

IndexOutOfBoundsException

NullPointerException

VirtualMachineError

IllegalArgumentException

ClassNotFoundException

LinkageError

IllegalArgumentException

Attempt to use a class that does not exist. If you try to run a nonexistent class using the java command or if your program were composed of, say, three class files, only two of which could be found

possible answers:

ArithmeticException

IndexOutOfBoundsException

NullPointerException

VirtualMachineError

IllegalArgumentException

ClassNotFoundException

LinkageError

ClassNotFoundException

A class has some dependency on another class, but the latter class has changed incompatibly after the compilation of the former class

possible answers:

ArithmeticException

IndexOutOfBoundsException

NullPointerException

VirtualMachineError

IllegalArgumentException

ClassNotFoundException

LinkageError

LinkageError

A Java exception is an instance of ___.

a. Throwable

b. Error

c. Exception

d. RuntimeException

e. NumberFormatException

a. Throwable

An instance of ___ describes system errors. If this type of error occurs, there is little you can do beyond notifying the user and trying to terminate the program gracefully.

a. Exception

b. RuntimeException

c. NumberFormatException

d. Error

e. Throwable

d. Error

An instance of ___ describes the errors caused by your program and external circumstances. These errors can be caught and handled by your program.

a. Exception

b. RuntimeException

c. NumberFormatException

d. Throwable

e. Error

a. Exception

An instance of ___ describes programming errors, such as bad casting, accessing an out-of-bounds array, and numeric errors.

a. RuntimeException

b. NumberFormatException

c. Throwable

d. Error

e. Exception

a. RuntimeException

An instance of ___ are unchecked exceptions. Select all that apply.

a. RuntimeException

b. Error

c. NumberFormatException

d. Exception

e. Throwable

a. RuntimeException

b. Error

c. NumberFormatException

What exception type does the following program throw?

public class Test {

public static void main(String[] args) {

System.out.println(1 / 0);

}

}

a. ArrayIndexOutOfBoundsException

b. ClassCastException

c. No exception

d. ArithmeticException

e. StringIndexOutOfBoundsException

d. ArithmeticException

What exception type does the following program throw?

public class Test {

public static void main(String[] args) {

int[] list = new int[5];

System.out.println(list[5]);

}

}

a. ClassCastException

b. ArrayIndexOutOfBoundsException

c. StringIndexOutOfBoundsException

d. No exception

e. ArithmeticException

b. ArrayIndexOutOfBoundsException

What exception type does the following program throw?

public class Test {

public static void main(String[] args) {

String s = "abc";

System.out.println(s.charAt(3));

}

}

a. ClassCastException

b. No exception

c. ArrayIndexOutOfBoundsException

d. ArithmeticException

e. StringIndexOutOfBoundsException

e. StringIndexOutOfBoundsException

What exception type does the following program throw?

public class Test {

public static void main(String[] args) {

Object o = new Object();

String d = (String)o;

}

}

a. ArrayIndexOutOfBoundsException

b. No exception

c. ClassCastException

d. StringIndexOutOfBoundsException

e. ArithmeticException

c. ClassCastException

What exception type does the following program throw?

public class Test {

public static void main(String[] args) {

Object o = null;

System.out.println(o.toString());

}

}

a. ArithmeticException

b. ArrayIndexOutOfBoundsException

c. StringIndexOutOfBoundsException

d. NullPointerException

e. ClassCastException

d. NullPointerException

What exception type does the following program throw?

public class Test {

public static void main(String[] args) {

Object o = null;

System.out.println(o);

}

}

a. ArrayIndexOutOfBoundsException

b. ArithmeticException

c. No exception

d. StringIndexOutOfBoundsException

e. NullPointerException

c. No exception

Which of the following is not an advantage of Java exception handling?

a. Exception handling improves performance.

b. Exception handling simplifies programming because the error-reporting and error-handling code can be placed at the catch block.

c. Java separates exception handling from normal processing tasks.

d. Exception handling makes it possible for the caller's caller to handle the exception.

a. Exception handling improves performance.

a program that automatically traverses the documents on the Web by following the hyperlinks

possible answers:

absolute file name

relative file name

web crawler

directory path

web crawler

the absolute file name without the complete directory path

possible answers:

absolute file name

relative file name

web crawler

directory path

relative file name

the absolute file name minus the relative file name

possible answers:

absolute file name

relative file name

web crawler

directory path

directory path

contains a file name with its complete path and drive letter

possible answers:

absolute file name

relative file name

web crawler

directory path

absolute file name

What are the reasons to create an instance of the File class? Select all that apply.

a. To read/write data from/to a file

b. To obtain the properties of the file such as whether the file can be read, written, or is hidden.

c. To determine whether the file exists.

d. To rename the file.

e. To delete the file.

b. To obtain the properties of the file such as whether the file can be read, written, or is hidden.

c. To determine whether the file exists.

d. To rename the file.

e. To delete the file.

Which of the following statements creates an instance of File on Windows for the file c:\temp.txt?

a. new File("c:/temp.txt")

b. new File("c://temp.txt")

c. new File("c:\\temp.txt")

d. new File("c:\temp.txt")

c. new File("c:\\temp.txt")

Which class contains the method for checking whether a file exists?

a. System

b. File

c. PrintWriter

d. Scanner

b. File

Which class do you use to write data into a text file?

a. PrintWriter

b. File

c. Scanner

d. System

a. PrintWriter

Which class do you use to read data from a text file?

a. Scanner

b. File

c. PrintWriter

d. System

a. Scanner

Which method can be used to write data?

a. rename

b. exist

c. print

d. close

c. print

Which method can be used to read a whole line from the file?

a. nextLine

b. nextInt

c. nextDouble

d. next

a. nextLine

Which method can be used to create an input object for file temp.txt?

a. new Scanner(temp.txt)

b. new Scanner("temp.txt")

c. new Scanner(new File("temp.txt"))

d. new Scanner(File("temp.txt"))

c. new Scanner(new File("temp.txt"))

Which method can be used to create an output object for file temp.txt? Select all that apply.

a. new PrintWriter(new File("temp.txt"))

b. new PrintWriter(temp.txt)

c. new PrintWriter("temp.txt")

d. new PrintWriter(File("temp.txt"))

a. new PrintWriter(new File("temp.txt"))

c. new PrintWriter("temp.txt")

Which of the following statements are correct? Select all that apply.

I:

try (PrintWriter output = new PrintWriter("output.txt")) {

output.println("Welcome to Java");

}

II:

try (PrintWriter output = new PrintWriter("output.txt");) {

output.println("Welcome to Java");

}

III:

PrintWriter output;

try (output = new PrintWriter("output.txt");) {

output.println("Welcome to Java");

}

IV:

try (PrintWriter output = new PrintWriter("output.txt");) {

output.println("Welcome to Java");

}

finally {

output.close();

}

a. I

b. III

c. IV

d. II

a. I

d. II

*Note: Do not select all for this one. You will lose credit, if so.*

Welcome to Java = I & II

Which of the following statements are correct?

I:

File file = new File("input.txt");

try (Scanner input = new Scanner(file)) {

String line = input.nextLine();

}

II:

try (File file = new File("input.txt");

Scanner input = new Scanner(file);) {

String line = input.nextLine();

}

III:

File file;

try (file = new File("input.txt");

Scanner input = new Scanner(file);) {

String line = input.nextLine();

}

IV:

File file;

Scanner input;

try (file = new File("input.txt");

input = new Scanner(file);) {

String line = input.nextLine();

}

a. II

b. IV

c. III

d. I

d. I

Input = I

Suppose you enter 34.3 57.8 789, then press the ENTER key. Analyze the following code.

Scanner input = new Scanner(System.in);

int v1 = input.nextInt();

int v2 = input.nextInt();

String line = input.nextLine();

a. After the last statement is executed, v1 is 34.

b. After the last statement is executed, line contains characters '7', '8', '9'.

c. The program has a runtime error because 34.3 is not an integer.

d. After the last statement is executed, line contains characters '7', '8', '9', '\n'.

c. The program has a runtime error because 34.3 is not an integer.

Suppose you enter 34.3 57.8 789, then press the ENTER key. Analyze the following code.

Scanner input = new Scanner(System.in);

double v1 = input.nextDouble();

double v2 = input.nextDouble();

String line = input.nextLine();

a. After the last statement is executed, line contains characters '7', '8', '9', '\n'.

b. After the last statement is executed, line contains characters ' ', '7', '8', '9', '\n'.

c. After the last statement is executed, line contains characters ' ', '7', '8', '9'.

d. After the last statement is executed, line contains characters '7', '8', '9'.

c. After the last statement is executed, line contains characters ' ', '7', '8', '9'.

Suppose you enter 34.3, the ENTER key, 57.8, the ENTER key. Analyze the following code. Select all that apply.

1 Scanner input = new Scanner(System.in);

2 double v1 = input.nextDouble();

3 double v2 = input.nextDouble();

4 String line = input.nextLine();

a. After line 4 is executed, line contains character "\n".

b. After line 2 is executed, v1 is 34.3.

c. After line 4 is executed, line contains an empty string.

d. After line 4 is executed, line is null.

e. After line 3 is executed, v2 is 57.8.

b. After line 2 is executed, v1 is 34.3.

c. After line 4 is executed, line contains an empty string.

e. After line 3 is executed, v2 is 57.8.

Suppose you enter 34.3, the ENTER key, 57.8, the ENTER key, abc, the Enter key. Analyze the following code. Select all that apply.

1 Scanner input = new Scanner(System.in);

2 double v1 = input.nextDouble();

3 double v2 = input.nextDouble();

4 String line = input.nextLine();

a. After line 2 is executed, v1 is 34.3.

b. After line 4 is executed, line contains character "abc".

c. After line 4 is executed, line is null.

d. After line 4 is executed, line contains an empty string.

e. After line 3 is executed, v2 is 57.8.

a. After line 2 is executed, v1 is 34.3.

d. After line 4 is executed, line contains an empty string.

e. After line 3 is executed, v2 is 57.8.

To create an InputStream to read from a file on a Web server, you use the method ___ in the URL class.

a. openStream();

b. getInputStream();

c. obtainInputStream();

d. connectStream();

a. openStream();

Which of the following class definitions defines a legal abstract class?

a. class A { abstract void unfinished() { } }

b. class A { abstract void unfinished(); }

c. abstract class A { abstract void unfinished(); }

d. public class abstract A { abstract void unfinished(); }

c. abstract class A { abstract void unfinished(); }

Which of the following declares an abstract method in an abstract Java class?

a. public abstract method();

b. public abstract void method();

c. public void abstract method();

d. public void method() {}

e. public abstract void method() {}

b. public abstract void method();

PAVM();

Which of the following statements regarding abstract methods is false?

a. An abstract class can have instances created using the constructor of the abstract class.

b. An abstract class can be extended.

c. A subclass of a non-abstract superclass can be abstract.

d. A subclass can override a concrete method in a superclass to declare it abstract.

e. An abstract class can be used as a data type.

a. An abstract class can have instances created using the constructor of the abstract class.

Which of the following statements regarding abstract methods is false?

a. Abstract classes have constructors.

b. A class that contains abstract methods must be abstract.

c. It is possible to declare an abstract class that contains no abstract methods.

d. An abstract method cannot be contained in a nonabstract class.

e. A data field can be declared abstract.

e. A data field can be declared abstract.

Suppose A is an abstract class, B is a concrete subclass of A, and both A and B have a no-arg constructor. Which of the following is correct? Select all that apply.

a. A a = new A();

b. A a = new B();

c. B b = new A();

d. B b = new B();

b. A a = new B();

d. B b = new B();

Assume Calendar calendar = new GregorianCalendar(). ____ returns the month of the year.

a. calendar.get(Calendar.MONTH)

b. calendar.get(Calendar.MONTH_OF_YEAR)

c. calendar.get(Calendar.WEEK_OF_MONTH)

d. calendar.get(Calendar.WEEK_OF_YEAR)

a. calendar.get(Calendar.MONTH)

Assume Calendar calendar = new GregorianCalendar(). ____ returns the week of the year.

a. calendar.get(Calendar.MONTH)

b. calendar.get(Calendar.MONTH_OF_YEAR)

c. calendar.get(Calendar.WEEK_OF_MONTH)

d. calendar.get(Calendar.WEEK_OF_YEAR)

d. calendar.get(Calendar.WEEK_OF_YEAR)

Assume Calendar calendar = new GregorianCalendar(). ____ returns the number of days in a month.

a. calendar.get(Calendar.MONTH)

b. calendar.get(Calendar.MONTH_OF_YEAR)

c. calendar.get(Calendar.WEEK_OF_MONTH)

d. calendar.get(Calendar.WEEK_OF_YEAR)

e. calendar.getActualMaximum(Calendar.DAY_OF_MONTH)

e. calendar.getActualMaximum(Calendar.DAY_OF_MONTH)

Which of the following is a correct interface?

a. interface A { void print() { }; }

b. abstract interface A { print(); }

c. abstract interface A { abstract void print() { };}

d. interface A { void print();}

d. interface A { void print();}

Which of the following are incorrect? Select all that apply.

a. An abstract class contains constructors.

b. The constructors in an abstract class should be protected.

c. The constructors in an abstract class are private.

d. You may declare a final abstract class.

e. An interface may contain constructors.

c. The constructors in an abstract class are private.

d. You may declare a final abstract class.

e. An interface may contain constructors.

____ is not a reference type.

a. A class type

b. An interface type

c. An array type

d. A primitive type

d. A primitive type