Question 1

Which of the following statements is true?
A) Each object (instance) of the class shares the class's instance variables.
B) Most instance-variable declarations are preceded with the keyword public, which is an access modifier.
C) Variables or methods declared with access modifier private are accessible only to methods of the class in which they're declared.
D) None of the above is true.

Accepted Answer

Option A is incorrect as each object (instance) of the class has its own copy of instance variables. Option B is incorrect as most instance-variable declarations are preceded with the keyword private, not public. Option C is correct as variables or methods declared with access modifier private are accessible only to methods of the class in which they're declared. Option D is incorrect as at least one option is true (Option C).

Question 2

Which of the following statements is true?
A) Local variables are automatically initialized.
B) Every instance variable has a default initial value-a value provided by Java when you do not specify the instance variable's initial value.
C) The default value for an instance variable of type String is void.
D) The argument types in the method call must be identical to the types of the corresponding parameters in the method's declaration.

Accepted Answer

Every instance variable has a default initial value provided by Java when you do not specify the instance variable's initial value. Local variables, on the other hand, do not have a default initial value and must be initialized before use. Option A is incorrect. Option C is false because String is a reference type, and its default initial value is null. Option D is a basic rule of method calling and is not related to variable initialization.

Question 3

Which of the following statements is false?
A) If a class does not define constructors, the compiler provides a default constructor with no parameters.
B) If you declare a constructor for a class, the compiler will not create a default constructor for that class.
C) The UML models constructors in the third compartment of a class diagram.
D) To distinguish a constructor from a class's operations, the UML places the word "constructor" between double quotes before the constructor's name.

Accepted Answer

The UML places the name of the constructor in the third compartment of a class diagram without double quotes. Therefore, statement D is false. Statements A, B, and C are true.

Question 4

Which of the following statements is false?
A) Variables declared in the body of a particular method are local variables and can be used only in that method.
B) A method's parameters are local variables of the method.
C) Every method's body is delimited by left and right braces ({ and }).
D) Keyword null indicates that a method will perform a task but will not return any information.

Accepted Answer

Keyword null indicates that a variable or object does not have a value assigned to it. It has nothing to do with a method's return type.

Question 5

Declaring instance variables ________ is known as data hiding or information hiding.
A) secure
B) private
C) static
D) masked

Accepted Answer

Declaring instance variables as private is known as data hiding or information hiding. It restricts access to the variables to only within the class, ensuring encapsulation and protecting the data from outside modification.

Question 6

When a method terminates, the values of its local variables are ________.
A) saved
B) copied
C) restored
D) lost

Accepted Answer

When a method terminates, the values of its local variables are lost. This means that the memory allocated to these variables is freed up and can be used for other purposes. The values of any parameters passed to the method are also lost. However, any values that were returned by the method are retained and can be used by the calling code.

Question 7

Which of the following statements is false?
A) The method's return type specifies the type of data returned to a method's caller.
B) Empty parentheses following a method name indicate that the method does not require any parameters to perform its task.
C) When a method that specifies a return type other than void is called and completes its task, the method must return a result to its calling method
D) Classes often provide public methods to allow the class's clients to set or get private instance variables; the names of these methods must begin with set or get.

Accepted Answer

This statement is false because while it is common practice for classes to provide public methods to set or get private instance variables, the names of these methods are not required to begin with set or get. They can be named according to the programmer's preference, as long as they follow appropriate naming conventions.

Question 8

Which of the following statements is false?
A) Scanner method next reads characters until any white-space character is encountered, then returns the characters as a String.
B) To call a method of an object, follow the object name with a comma, the method name and a set of parentheses containing the method's arguments.
C) A class instance creation expression begins with keyword new and creates a new object.
D) A constructor is similar to a method but is called implicitly by the new operator to initialize an object's instance variables at the time the object is created.

Accepted Answer

The statement "To call a method of an object, follow the object name with a comma, the method name and a set of parentheses containing the method's arguments" is false. To call a method of an object, you should use the dot notation: objectName.methodName(arguments).

Question 9

Which of the following statements is false?
A) Most classes you'll use in Java programs must be imported explicitly.
B) There's a special relationship between classes that are compiled in the same directory. By default, such classes are considered to be in the same package-known as the default package.
C) Classes in the same package are implicitly imported into main.
D) An import declaration is not required when one class in a package uses another in the same package.

Accepted Answer

Classes in the same package are not implicitly imported into main. They are only implicitly imported into other classes in the same package.

Question 10

Which of the following statements is false?
A) Each class declaration that begins with the access modifier private must be stored in a file that has the same name as the class and ends with the .java filename extension.
B) Every class declaration contains keyword class followed immediately by the class's name.
C) Class, method and variable names are identifiers.
D) An object has attributes that are implemented as instance variables and carried with it throughout its lifetime.

Accepted Answer

Private access modifier only restricts access to the class within the same file, but the file name does not need to match the class name.

Question 11

Which of the following statements is true?
A) Constructors can specify parameters and return types.
B) Constructors can specify parameters but not return types.
C) Constructors cannot specify parameters but can specify return types.
D) Constructors can specify neither parameters nor return types.

Accepted Answer

Constructors can specify parameters, but they do not have return types. This is because the main purpose of a constructor is to initialize an object and prepare it for use, rather than to return a value.

Question 12

Which of the following statements is false?
A) The javac command can compile multiple classes at once; simply list the source-code filenames after the command with each filename separated by a comma from the next.
B) If the directory containing the app includes only one app's files, you can compile all of its classes with the command javac *.java.
C) The asterisk (*) in javac *.java indicates that all files in the current directory ending with the filename extension ".java" should be compiled.
D) All of the above are true.

Accepted Answer

The statement "The javac command can compile multiple classes at once; simply list the source-code filenames after the command with each filename separated by a comma from the next" is true. However, the statement in option B is not entirely false, but it is not always true. It depends on whether all of the app's classes are contained in the same directory or not. If there are multiple directories containing classes, this command will only compile the classes in the current directory. Option C is true. Therefore, the correct answer is A.

Question 13

Java requires a ________ call for every object that's created.
A) constructor
B) destructor
C) parameterless
D) parameterized

Accepted Answer

Java requires a constructor call for every object that's created. The constructor initializes the object and sets its initial state.

Question 14

An import declaration is not required if you always refer to a class with its ________ name, which includes its package name and class name.
A) compile-time
B) default package
C) paired
D) fully qualified name

Accepted Answer

A fully qualified name includes both the package name and the class name of a class, and can be used to refer to the class without the need for an import declaration.

Question 15

Which of the following statements is true?
A) The UML models a parameter of an operation by listing the parameter name, followed by a colon and the parameter value between the parentheses after the operation name.
B) The UML indicates an operation's return type by placing a colon and the return value after the parentheses following the operation name.
C) UML class diagrams do not specify return types for operations that do not return values.
D) Declaring instance variables public is known as data hiding or information hiding.

Accepted Answer

The answer of Which of the following statements is true?
A)...

Question 16

Each class you create becomes a new ________ that can be used to declare variables and create objects.
A) package
B) instance
C) library
D) type.

Accepted Answer

A class defines a new type that can be used to declare variables and create objects, so the best choice is D, type. A package is used to group related classes, a library is a collection of pre-compiled code that can be reused in different programs, and an instance is a single occurrence of a class.

Question 17

Which of the following statements is false?
A) In the UML, each class is modeled in a class diagram as a rectangle with three compartments. The top one contains the class's name centered horizontally in boldface. The middle one contains the class's attributes, which correspond to instance variables in Java. The bottom one contains the class's operations, which correspond to methods and constructors in Java.
B) UML represents instance variables as an attribute name, followed by a colon and the type.
C) Private attributes are preceded by the keyword private in the UML.
D) The UML models operations by listing the operation name followed by a set of parentheses. A plus sign (+) in front of the operation name indicates that the operation is a public.

Accepted Answer

In UML, access modifiers are not represented by keywords like "private" or "public" but by symbols. A minus sign (-) represents private attributes or operations, and a plus sign (+) represents public ones.

Question 18

You can declare new classes as needed; this is one reason Java is known as a(n) ________ language.
A) portable
B) incremental
C) extensible
D) virtual

Accepted Answer

Java is known as an extensible language because it allows programmers to create and declare new classes as needed, thus extending the functionality of the language beyond its built-in classes and libraries.

Question 19

If a class does not define constructors, the compiler provides a default constructor with no parameters, and the class's instance variables are initialized to ________.
A) zero
B) null
C) their default values.
D) false

Accepted Answer

When a class does not define any constructors, the compiler provides a default constructor with no parameters. The instance variables of the class are then initialized to their default values, which depend on their data type. For example, instance variables of type int are initialized to 0, instance variables of type boolean are initialized to false, and instance variables of object types are initialized to null. Therefore, the best choice is C, which specifies that the instance variables are initialized to their default values.

Question 20

A static method can ________.
A) call only other static methods of the same class directly
B) manipulate only static fields in the same class directly
C) be called using the class name and a dot (.)
D) All of the above.

Accepted Answer

All of the above statements are true about static methods. They can only call other static methods and manipulate static fields, and they are called using the class name and a dot (.).

Quiz 7: Introduction to Classes and Objects

Which of the following statements is true?

Which of the following statements is true?

Which of the following statements is false?

Which of the following statements is false?

Declaring instance variables ________ is known as data hiding or information hiding.

When a method terminates, the values of its local variables are ________.

Which of the following statements is false?

Which of the following statements is false?

Which of the following statements is false?

Which of the following statements is false?

Which of the following statements is true?

Which of the following statements is false?

Java requires a ________ call for every object that's created.

An import declaration is not required if you always refer to a class with its ________ name, which includes its package name and class name.

Which of the following statements is true?

Each class you create becomes a new ________ that can be used to declare variables and create objects.

Which of the following statements is false?

You can declare new classes as needed; this is one reason Java is known as a(n) ________ language.

If a class does not define constructors, the compiler provides a default constructor with no parameters, and the class's instance variables are initialized to ________.

A static method can ________.