Deck 8: User-Defined Classes and Adts

Question 1

An accessor method of a class first accesses the values of the data members of the class and then changes the values of the data members.

Answer 1

False

Question 2

In deep copying, each reference variable refers to its own object.

Answer 2

True

Question 3

Given the declaration public class MyClass {private int x; public void print() {System.out.println("x = " + x);} private void setX(int y) {x = y;}} MyClass myObject = new MyClass(); The following statement is legal. myObject.print();

Answer 3

True

Question 4

When no object of the class type is instantiated, static data members of the class fail to exist.

Question 5

Members of a class are usually classified into three categories: public, private, and static.

Question 6

If the object is created in the definition of a method of the class, then the object can access both the public and private members of the class.

Question 7

Not every user-defined class can override the default definition of the method toString because it is provided by Java.

Question 8

The components of a class are called fields.

Question 9

Constructors are called like any other method.

Question 10

Modifiers are used to alter the behavior of the class.

Question 11

The methods of a class must be public.

Question 12

A constructor has no type and is therefore a void method.

Question 13

If a member of a class is a private method, you can access it outside the class.

Question 14

In shallow copying, each reference variable refers to its own object.

Question 15

Given the declaration public class MyClass {private int x; public void print() {System.out.println("x = " + x);} private void setX(int y) {x = y;}} MyClass myObject = new MyClass(); The following statement is legal. myObject.setX(10);

Question 16

The built-in operation that is valid for classes is the dot operator.

Question 17

The non-static methods of a class are called instance methods.

Question 18

The default constructor executes when an object is instantiated and initialized using an existing object.

Question 19

The method finalize automatically executes when the class object goes out of scope.

Question 20

A class and its members can be described graphically using Unified Modeling Language (UML) notation.

Question 21

Which of the following is a constructor without parameters?

A) copy constructor
C) finalizer
B) default constructor
D) modifier

Question 22

Which of the following would be a default constructor for the class MysteryClass shown in the accompanying figure?

A) public MysteryClass(){ setData(0, 0.0); }
B) public MysteryClass(0, 0.0) { setData(); }
C) public MysteryClass(0) { setData(0, 0.0); }
D) private MysteryClass(10){ setData(); }

Question 23

Class members consist of all of the following EXCEPT ____.

A) named constants
C) pre-defined methods
B) variable declarations
D) methods

Question 24

The abstract data type specifies the logical properties and the implementation details.

Question 25

According to the UML class diagram in the accompanying figure, which method is public and doesn't return anything?

A) getCopy()
C) equals(MysteryClass)
B) print()
D) doubleFirst()

Question 26

In Java, the reference this is used to refer to only the methods, not the instance variables of a class.

Question 27

Constructors have the same name as the ____.

A) member methods
C) class
B) data members
D) package

Question 28

Consider the following class definition. public class Cylinder {private double baseRadius; private double height; public Cylinder () {baseRadius = 0; height = 0;} public Cylinder (double l, double h) {baseRadius = l; height = h;} public void set(double r, double h) {baseRadius = r; height = h;} public String toString() {return (baseRadius + " " + height);} public double SurfaceArea() {return 2 * 3.14 * baseRadius * height;} public double volume() {return 3.14 * baseRadius * baseRadius * height;}} Suppose that you have the following declaration. Cylinder cyl = new Cylinder(1.5, 10); Which of the following sets of statements are valid in Java? (i) cyl.surfaceArea(); cyl.volume(); cyl.print(); (ii) print(cyl.surfaceArea); print(cyl.volume());

A) Only (i)
C) Both (i) and (ii)
B) Only (ii)
D) None of these

Question 29

A mutator method of a class changes the values of the data members of the class.

Question 30

Which of the following class definitions is correct in Java? (i) public class Employee {private String name; private double salary; private int id; public Employee() {name = ""; salary = 0.0; id = 0;} public Employee(String n, double s, int i) {name = n; salary = s; id = i;} public void print() {System.out.println(name + " " + id + " " + salary);}} (ii) public class Employee {private String name; private double salary; private int id; public void Employee() {name = ""; salary = 0.0; id = 0;} public void Employee(String n, double s, int i) {name = n; salary = s; id = i;} public void print() {System.out.println(name + " " + id + " " + salary);}}

A) Only (i)
C) Both (i) and (ii)
B) Only (ii)
D) Neither is correct

Question 31

In ____ copying, each reference variable refers to its own object.

A) shallow
C) method
B) deep
D) object

Question 32

Consider the following statements. public class Circle {private double radius; public Circle() {radius = 0.0;} public Circle(double r) {radius = r;} public void set(double r) {radius = r;} public void print() {System.out.println(radius + " " + area + " " + circumference);} public double area() {return 3.14 * radius * radius;} public double circumference() {return 2 * 3.14 * radius;}} Circle myCircle = new Circle(); double r; Which of the following statements are valid in Java? (Assume that console is Scanner object initialized to the standard input device.) (i) r = console.nextDouble(); myCircle.area = 3.14 * r * r; System.out.println(myCircle.area); (ii) r = console.nextDouble(); myCircle.set(r); System.out.println(myCircle.area());

A) Only (i)
C) Both (i) and (ii)
B) Only (ii)
D) None of these

Question 33

Consider the following class definition. public class Rectangle {private double length; private double width; public Rectangle() {length = 0; width = 0;} public Rectangle(double l, double w) {length = l; width = w;} public void set(double l, double w) {length = l; width = w;} public void print() {System.out.println(length + " " + width);} public double area() {return length * width;} public double perimeter() {return 2 * length + 2 * width;}} Which of the following statements correctly instantiates the Rectangle object myRectangle? (i) myRectangle = new Rectangle(12.5, 6); (ii) Rectangle myRectangle = new Rectangle(12.5, 6); (iii) class Rectangle myRectangle = new Rectangle(12.5, 6);

A) Only (i)
C) Only (iii)
B) Only (ii)
D) Both (ii) and (iii)

Question 34

Which of the following is used to allocate memory for the instance variables of an object of a class?

A) the reserved word public
C) the operator new
B) the reserved word static
D) the operator +

Question 35

According to the UML class diagram in the accompanying figure, which of the following is a private member of the class MysteryClass?

A) doubleFirst
C) second
B) MysteryClass
D) print

Question 36

Consider the following statements. public class Rectangle {private double length; private double width; public Rectangle() {length = 0; width = 0;} public Rectangle(double l, double w) {length = l; width = w;} public void set(double l, double w) {length = l; width = w;} public void print() {System.out.println("Length = " + length + "; Width = " + width + "\n" + + " Area = " + area() + "; Perimeter = " + perimeter());} public double area() {return length * width;} public void perimeter() {return 2 * length + 2 * width;} public void makeCopy(Rectangle otherRect) {length = otherRect.length; width = otherRect.width}} Rectangle tempRect = new Rectangle(14, 10); Rectangle newRect = new Rectangle(9, 5); What are the values of the instance variables of newRect after the following statement execute? newRect.makeCopy(tempRect);

A) length = 14; width = 10
B) length = 9; width = 5
C) length = 14; width = 5
D) None of these

Question 37

According to the UML class diagram in the accompanying figure, which of the following is a data member?

A) MysteryClass
C) second
B) print()
D) getFirst

Question 38

Every object has access to a reference to itself.

Question 39

What is the default definition of the method toString?

A) There is no default definition; you must define the method yourself.
B) It creates a string that is the name of the object's class, followed by the hash code of the object.
C) It creates a string that is the name of the program.
D) It creates a string that is the name of the package, followed by the name of the class, followed by the hash of the object.

Question 40

Classes that are defined within other classes are called inside classes.

Question 41

Which of the following words indicates an object's reference to itself?

A) this
C) public
B) that
D) protected

Question 42

How many constructors are present in the class definition in the accompanying figure?

A) zero
C) two
B) one
D) three

Question 43

What does the default constructor do in the class definition in the accompanying figure?

A) Sets the value of x to 0
B) Sets the value of z to 1
C) Sets the value of x to 0 and the value of z to 1
D) There is no default constructor.

Question 44

What is the main use of inner classes?

A) To alter the behavior of the outer class
B) To handle events
C) To implement cascaded method calls
D) To provide information hiding

Question 45

How many finalizers can a class have?

A) zero
C) two
B) one
D) Any number

Question 46

Based on the class in the accompanying figure, which of the following statements is illegal?

A) Secret.incrementY();
B) Secret.count++;
C) Secret.z++;
D) Secret secret = new Secret(4);

Question 47

ADTs illustrate the principle of ____.

A) information hiding
C) encapsulation
B) privacy
D) overloading

Question 48

When does the method finalize execute?

A) When the class object is created
B) At the start of every program
C) At the end of every program
D) When the class object goes out of scope

Question 49

What might the heading of the copy constructor for the class in the accompanying figure look like?

A) public Secret(Secret s)
B) private copySecret()
C) Secret copySecret = new Secret()
D) public copySecret(int a, int b)

Question 50

Suppose that Book is class with two instance variables-name of type String and numOfBooks of type int. Which of the following would be appropriate syntax for the heading of a copy constructor for the class called Book?

A) public Book(String n, int num)
B) public Book()
C) public Book(Book b)
D) public copyBook(String n, int num)