Question 1

A constructor is invoked when ___ to create an object.

Accepted Answer

The constructor is invoked when the new keyword is used to create an object. The other options do not directly involve invoking the constructor.

Question 2

Which statement calls a constructor with no construction parameters?

Accepted Answer

In Java, to call a constructor with no construction parameters, we simply use the format "ClassName variableName = new ClassName();" as shown in option A. Option B is incorrect syntax as it is missing the parentheses after the class name. Option C is not valid Java syntax as it is missing the "new" keyword. Option D is incorrect as not all constructors require construction parameters.

Question 3

Consider the following code snippet:
Public class Coin
{
Private String coinName;
Private int coinValue;
Public Coin()
{
}
) . .
}
Which statement reflects the action performed when the constructor to Coin is called?

Accepted Answer

When the constructor to Coin is called, the variables coinName and coinValue will be initialized to their default values which are null for the String type and 0 for the int type. Therefore, option D is the correct answer.

Question 4

If you do not provide a constructor in a class, which of the following is correct?

Accepted Answer

If a constructor is not provided in a class, the compiler will automatically generate a default constructor with no arguments. This default constructor will initialize all instance variables to their default values.

Question 5

Consider the following code snippet:
Public class Employee
{
Private String empID;
Private boolean hourly;
Public Employee()
{
}
) . .
}
Which statement reflects the action performed when the constructor to Employee is called?

Accepted Answer

In Java, instance variables of a class are initialized to default values if not explicitly initialized. For a String, the default is null, and for a boolean, the default is false.

Question 6

Consider the following code snippet:
Public int getSalary(String empNum)
{ ) . . }
Which of the following statements is correct?

Accepted Answer

empNum is an explicit parameter as it is passed as an argument to the method. It is not an implicit parameter that is automatically passed by the system. An implicit parameter is usually the object on which the method is invoked if it is an instance method. empNum is also not the object on which this method is invoked since there is no reference to the keyword "this". It is also not an instance variable since it is not declared at the class level but passed as a parameter to the method.

Question 7

The object on which a method is invoked is called the ____.

Accepted Answer

The object on which a method is invoked is known as the implicit parameter. It is implicit because it is not explicitly named in the method call, but it is assumed to exist since the method is being called on an object.

Question 8

Which of the following lists the correct order of items in an instance method declaration?

Accepted Answer

The correct order of items in an instance method declaration is modifiers, a return type, a method name, and a list of the parameters (if any). The modifiers can be things like public or private, the return type is what the method will return (if anything), the method name is what you'll call the method, and the list of parameters (if any) are what the method needs in order to perform its task.

Question 9

Which of the following statements about constructors is NOT correct?

Accepted Answer

A constructor can have construction parameters, but it can also have no parameters. In fact, a constructor with no parameters is called a default constructor.

Question 10

Consider the following code snippet:
Public class Vehicle
{
Private String type;
Public String Vehicle(String type)
{
) . .
}
}
What is wrong with this code?

Accepted Answer

The constructor in Java should not have a return type. In the given code, the constructor is incorrectly defined with a return type of String.

Question 11

Consider the following code snippet:
Public class Vehicle
{
Private String type;
Private int numAxles;
Public Vehicle()
{
}
) . .
}
Which statement reflects the action performed when the constructor to Vehicle is called?

Accepted Answer

In Java, instance variables of a class are initialized to default values if not explicitly initialized. For object references like String, the default is null, and for int, the default is 0.

Question 12

Which of the following statements about classes is correct?

Accepted Answer

It is considered a best practice to keep instance variables private as this enforces encapsulation and prevents direct manipulation of the data. However, some instance methods may need to be public in order to be accessed from outside the class. This allows for better control and management of the class's members and behavior.

Question 13

Which of the following statements about instance methods is correct?

Accepted Answer

Instance methods are typically declared as private if they are intended to be helper methods, meaning they are used internally within the class and not meant to be accessed from outside the class.

Question 14

Input to a method enclosed in parentheses after the method name is known as ____.

Accepted Answer

Input to a method enclosed in parentheses after the method name is known as explicit parameters. Implicit parameters refer to the parameters that are not explicitly specified in the method signature but are present in the context of the method, such as instance variables or global variables. Interfaces define a set of methods that a class can implement. Return values are the values that a method sends back to the calling program after it has completed its task.

Question 15

Consider the following code snippet:
Public class Vehicle
{
Private String type;
Private int numAxles;
Public Vehicle(String vehicleType, int VehicleAxles)
{ ) . . }
}
Which of the following statements can be used to create an object of type Vehicle?

Accepted Answer

Option A is incorrect because the constructor defined in the Vehicle class takes two arguments. Option B is incorrect because the order of arguments passed in is incorrect (it should be the vehicle type first and the axle number second). Option C is also incorrect because the second argument should be an integer, not a string. Option D is the correct choice because it matches the constructor defined in the Vehicle class where the first argument is a string and the second is an integer.

Question 16

You are creating a class named Vessel. Which statement correctly declares a constructor for this class?

Accepted Answer

To declare a constructor for a class in Java, the constructor method must have the same name as the class. In this case, the class is named Vessel. Therefore, the correct syntax for a constructor would be "public Vessel()", which would create a public constructor for the Vessel class. Choice B is incorrect because the "void" keyword indicates that the method does not return a value, and constructors cannot have a return type. Choice C is incorrect because it is missing the access specifier keyword "public", which would make the constructor accessible to other classes. Choice D is incorrect because "new Vessel()" is not a constructor declaration, but rather an instantiation of the Vessel class using the default constructor.

Question 17

Which of the following statements about constructors is correct?

Accepted Answer

A constructor must have the same name as the class. Option A is incorrect as a class can have multiple constructors with different parameters. Option B is incorrect as constructors do not have a return type. Option C is incorrect as the default constructor is provided by the compiler if no constructors are defined by the programmer.

Question 18

You are creating a class named Employee. Which statement correctly declares a constructor for this class?

Accepted Answer

The correct syntax for declaring a constructor in Java is to use the same name as the class itself. The constructor should also have the access modifier of either public, protected, or private. Since we want the constructor to be accessible from outside the class, we should use the public modifier. Therefore, the correct constructor declaration for the Employee class would be: public Employee(). Option A satisfies all these conditions. Option B is incorrect because constructors should not have a return type, and void is a return type. Option C is also incorrect because it does not have an access modifier, and constructors need an access modifier. Option D is incorrect because it tries to instantiate a new object within the constructor, which is not allowed.

Question 19

Consider the following code snippet:
Public class Vessel
{
Private String type;
Public String Vessel(String type)
{
) . .
}
}
What is wrong with this code?

Accepted Answer

The constructor should not have a return type. In the code, "Public String Vessel(String type)" incorrectly declares a return type "String" for the constructor.

Question 20

Consider the following code snippet:
Public int getCoinValue(String coinName)
{ ) . . }
Which of the following statements is correct?

Accepted Answer

In the given code snippet, coinName is explicitly specified as a parameter to the getCoinValue method. An explicit parameter is a variable that is declared as part of a method's parameter list and is used to pass data to the method.

Quiz 8: Objects and Classes

A constructor is invoked when ___ to create an object.

Which statement calls a constructor with no construction parameters?

Consider the following code snippet: Public class Coin { Private String coinName; Private int coinValue; Public Coin() { } ) . . } Which statement reflects the action performed when the constructor to Coin is called?

If you do not provide a constructor in a class, which of the following is correct?

Consider the following code snippet: Public class Employee { Private String empID; Private boolean hourly; Public Employee() { } ) . . } Which statement reflects the action performed when the constructor to Employee is called?

Consider the following code snippet: Public int getSalary(String empNum) { ) . . } Which of the following statements is correct?

The object on which a method is invoked is called the ____.

Which of the following lists the correct order of items in an instance method declaration?

Which of the following statements about constructors is NOT correct?

Consider the following code snippet: Public class Vehicle { Private String type; Public String Vehicle(String type) { ) . . } } What is wrong with this code?

Consider the following code snippet: Public class Vehicle { Private String type; Private int numAxles; Public Vehicle() { } ) . . } Which statement reflects the action performed when the constructor to Vehicle is called?

Which of the following statements about classes is correct?

Which of the following statements about instance methods is correct?

Input to a method enclosed in parentheses after the method name is known as ____.

Consider the following code snippet: Public class Vehicle { Private String type; Private int numAxles; Public Vehicle(String vehicleType, int VehicleAxles) { ) . . } } Which of the following statements can be used to create an object of type Vehicle?

You are creating a class named Vessel. Which statement correctly declares a constructor for this class?

Which of the following statements about constructors is correct?

You are creating a class named Employee. Which statement correctly declares a constructor for this class?

Consider the following code snippet: Public class Vessel { Private String type; Public String Vessel(String type) { ) . . } } What is wrong with this code?

Consider the following code snippet: Public int getCoinValue(String coinName) { ) . . } Which of the following statements is correct?