Question 1

A class that contains public methods that can change the data in the object of a class is called a/an:
A)mutable class
B)immutable class
C)invariant class
D)none of the above

Accepted Answer

A mutable class is one that can be modified by its public methods. This means that the data in the object can be changed and updated through the use of these methods. In contrast, an immutable class does not allow its internal data to be changed once it has been created, while an invariant class is one that does not allow any changes to its internal state. Therefore, the best choice is A) mutable class.

Question 2

When you use the assignment operator with variables of a class type,you are assigning a:
A)value
B)primitive type
C)local variable
D)reference

Accepted Answer

When you use the assignment operator with variables of a class type, you are assigning a reference to that object. This means that you are copying the memory address of the object, rather than copying the object itself. Any changes made to the original object will be reflected in the copy, and vice versa, because they both refer to the same object in memory.

Question 3

A condition that allows a programmer to circumvent the private modifier and change the private instance variable is called:
A)a copy constructor
B)a privacy leak
C)a class invariant
D)an anonymous object

Accepted Answer

A privacy leak is a programming error that occurs when a programmer can indirectly manipulate a private variable. It is considered a security vulnerability and can lead to unexpected behavior and bugs in the code. A copy constructor is a method for creating a new object that is a copy of an existing object. A class invariant is a property that is always true for all instances of a class. An anonymous object is an object that has no name and is created and used only once. None of these options describe a condition that allows a programmer to circumvent the private modifier.

Question 4

The conversion from an object of a wrapper class to a value of its associated primitive type is called:
A)Boxing
B)Unboxing
C)Converting
D)Reinstantiating

Accepted Answer

Conversion from an object of a wrapper class to a value of its associated primitive type is called unboxing, as it involves extracting the value from the wrapper object and returning it as a primitive type. Boxing, on the other hand, involves wrapping a primitive value in a wrapper class. Converting and reinstantiating do not accurately describe this process.

Question 5

The Math method that returns the nearest whole number that is greater than or equal to its argument is:
A)round
B)ceil
C)floor
D)all of the above

Accepted Answer

The ceil method returns the smallest integer that is greater than or equal to the input argument. The round method rounds the input argument to the nearest integer, which may be either greater than or less than the input argument. The floor method returns the largest integer that is less than or equal to the input argument. Therefore, only the ceil method satisfies the condition of returning the nearest whole number that is greater than or equal to the input argument.

Question 6

A copy constructor has _________ parameters.
A)zero
B)one
C)two
D)three

Accepted Answer

A copy constructor has one parameter which is a reference to the same class type. It is used to make a new object that is a copy of an existing object of the same class.

Question 7

All of these are methods of Java's Math class except:
A)pow
B)min
C)random
D)toString

Accepted Answer

The methods pow, min, and random are all valid methods in Java's Math class. However, toString is not a method in Java's Math class, but rather a method inherited from the Object class.

Question 8

Only ______ copy/copies of a static variable are available to objects of a class.
A)one
B)two
C)three
D)none of the above

Accepted Answer

Only one copy of a static variable exists in memory, regardless of the number of objects created from the class.

Question 9

The program included in the Java SDK that allows a programmer to separate the class interface from the class implementation is called:
A)javac
B)java
C)javadoc
D)none of the above

Accepted Answer

The program included in the Java SDK that allows a programmer to separate the class interface from the class implementation is called Javadoc. Javadoc is a tool used for generating API documentation in HTML format from Java source code. It extracts the documentation comments from the Java source code and produces an HTML document that describes the API. It helps the programmer to understand the purpose, data types, and methods of the class without having to read the source code.

Question 10

Converting from a value of primitive type to a corresponding object of its associated wrapper class is called:
A)Boxing
B)Unboxing
C)Converting
D)Reinstantiating

Accepted Answer

Boxing is the process of converting a value of a primitive type (e.g. int, char, boolean) to its corresponding object of its associated wrapper class (e.g. Integer, Character, Boolean). This is done using the valueOf() method of the wrapper class. For example, boxing an int value of 5 would result in an Integer object with a value of 5.

Question 11

A static method is one that can be used with a _____________.
A)instance variable
B)local variable
C)global variable
D)the class name as a calling object

Accepted Answer

A static method is one that can be called using the class name as the calling object, without the need for an instance of the class to be created. It does not have access to instance variables, local variables or global variables, as it is not tied to a specific instance of the class. Therefore, option D is the best choice.

Question 12

A main method can be placed inside a class definition.

Accepted Answer

The main method is commonly placed inside a class definition in Java programming.

Question 13

The method trim of the String class trims off:
A)Leading white space
B)Trailing white space
C)Leading and trailing white space
D)Blanks

Accepted Answer

The method trim() of the String class trims off both leading and trailing white spaces.

Question 14

To create a package,you must add a package statement at the ____________ of each class file.
A)beginning
B)end
C)before each method signature
D)after the import statements

Accepted Answer

The package statement should be added at the beginning of each class file to indicate the name of the package to which the class belongs. This is necessary for organizing and identifying the classes within a project and for preventing naming conflicts between classes from different packages. Adding package statement after import statements or before the method signature is not valid syntax.

Question 15

null can be used:
A)to indicate a variable has no real value
B)in a Boolean expression with ==
C)as a placeholder
D)all of the above

Accepted Answer

Null can be used to indicate a variable has no value, to compare with == in a Boolean expression, and as a placeholder in certain contexts. Therefore, all the options given are correct.

Question 16

Javadoc requires a comment to be delimited by _________ to be included in the extracted class interface.
A)// //
B)/* */
C)/** */
D)" "

Accepted Answer

Javadoc requires a comment to be delimited by /** and */ to be included in the extracted class interface.

Question 17

An example of secondary memory is:
A)RAM
B)ROM
C)hard disk
D)all of the above

Accepted Answer

Secondary memory refers to non-volatile storage devices that retain data even when the power is off. RAM and ROM are both types of primary memory, which are volatile and lose data when the power is off. Therefore, the only option that fits the definition of secondary memory is the hard disk.

Question 18

All of the following are wrapper classes except:
A)String
B)Integer
C)Character
D)Double

Accepted Answer

Wrapper classes provide a way to use primitive data types (int, char, double, etc.) as objects. The classes Integer, Character, and Double are all examples of wrapper classes for their respective primitive types. String, however, is not a wrapper class but a class for representing sequences of characters and is not associated with a primitive type.

Question 19

In a static method,you may use the this parameter either explicitly or implicitly.

Accepted Answer

In a static method, the "this" keyword cannot be used, as static methods are not associated with any particular instance of the class.

Question 20

Static variables are often used:
A)in arithmetic expressions
B)to communicate between objects
C)within looping structures
D)all of the above

Accepted Answer

Static variables are often used to communicate between objects as they retain their value across multiple function calls and can be accessed by different instances of the same class. They are not typically used in arithmetic expressions or within looping structures.

Quiz 5: Defining Classes II

A class that contains public methods that can change the data in the object of a class is called a/an:

When you use the assignment operator with variables of a class type,you are assigning a:

A condition that allows a programmer to circumvent the private modifier and change the private instance variable is called:

The conversion from an object of a wrapper class to a value of its associated primitive type is called:

The Math method that returns the nearest whole number that is greater than or equal to its argument is:

A copy constructor has _________ parameters.

All of these are methods of Java's Math class except:

Only ______ copy/copies of a static variable are available to objects of a class.

The program included in the Java SDK that allows a programmer to separate the class interface from the class implementation is called:

Converting from a value of primitive type to a corresponding object of its associated wrapper class is called:

A static method is one that can be used with a _____________.

A main method can be placed inside a class definition.

The method trim of the String class trims off:

To create a package,you must add a package statement at the ____________ of each class file.

null can be used:

Javadoc requires a comment to be delimited by _________ to be included in the extracted class interface.

An example of secondary memory is:

All of the following are wrapper classes except:

In a static method,you may use the this parameter either explicitly or implicitly.

Static variables are often used: