Question 1

An instance of a class does not have to exist in order for values to be stored in a class's static fields.

Accepted Answer

Static fields are associated with the class rather than with any particular instance of the class. Therefore, values can be stored in these fields without the need for an instance of the class to be created.

Question 2

The whole-part relationship created by object aggregation is more often called:
A) a has a relationship
B) an inner class relationship
C) an extra class relationship
D) an inside class relationship

Accepted Answer

The whole-part relationship created by object aggregation is commonly referred to as "a has a relationship." This is because the whole object (the "has") contains a part object.

Question 3

If you write a toString method to display the contents of an object, object1, for a class, Class1, then the following two statements are equivalent:
System.out.println(object1);
System.out.println(object1.toString());

Accepted Answer

When you call System.out.println on an object, it implicitly calls the object's toString method. Therefore, the two statements are equivalent.

Question 4

A single copy of a class's static field is shared by all instances of the class.

Accepted Answer

Static fields belong to the class and not individual instances, therefore all instances share the same value of the static field.

Question 5

Look at the following declaration: enum Tree { OAK, MAPLE, PINE }
What is the ordinal value of the MAPLE enum constant?
A) 0
B) 1
C) 2
D) 3
E) Tree.MAPLE

Accepted Answer

In Java, the ordinal value of the first enum constant is always 0, the second one is 1, and so on. Therefore, MAPLE has an ordinal value of 1.

Question 6

Enumerated types have this method, which returns the position of an enum constant in the declaration list.
A) toString
B) position
C) ordinal
D) location

Accepted Answer

The `ordinal` method in Java's enum types returns the position of an enum constant in its enum declaration, starting from zero.

Question 7

If you attempt to perform an operation with a null reference variable:
A) the resulting operation will always be zero
B) the results will be unpredictable
C) the program will terminate
D) Java will create an object to reference the variable

Accepted Answer

Attempting to perform an operation with a null reference variable in Java will result in a NullPointerException, causing the program to terminate unless the exception is properly handled.

Question 8

A declaration for an enumerated type begins with this key word.
A) enumerated
B) enum_type
C) enum
D) ENUM

Accepted Answer

The key word for declaring an enumerated type is "enum."

Question 9

The this key word is the name of a reference variable that is available to all static methods.

Accepted Answer

The "this" keyword refers to the current object and is only available in non-static methods, not static methods.

Question 10

Assuming the following declaration exists: enum Tree { OAK, MAPLE, PINE }
What will the following code display?
System.out.println(Tree.OAK);
A) Tree.OAK
B) 0
C) 1
D) OAK
E) Nothing. This statement will cause an error.

Accepted Answer

The code will display the name of the enum constant, which in this case is "OAK". It will not display the index value of the enum constant or cause an error.

Question 11

Both instance fields and instance methods are associated with a specific instance of a class, and they cannot be used until an instance of the class is created.

Accepted Answer

Instance fields and methods are specific to an object of a class, so they cannot be accessed until an instance of the class is created.

Question 12

When an object is passed as an argument, it is actually a reference to the object that is passed.

Accepted Answer

When an object is passed as an argument in Python, it is actually a reference to the object that is being passed, not a copy of the object itself. This means that changes made to the object within the function will also affect the original object outside the function.

Question 13

If the following is from the method section of a UML diagram, which of the following statements is TRUE?
+ add(object2:Stock): Stock
A) This is a private method named add that accepts and returns objects of the Stock class.
B) This is a private method named Stock that adds two objects.
C) This is a public method named add that accepts and returns references to objects in the Stock class.
D) This is a public method named Stock that adds two objects.

Accepted Answer

The + symbol denotes a public method, and the method name is "add". The parameter is an object of the "Stock" class, and the method returns an object of the "Stock" class. Therefore, option C is correct. Option A is incorrect because it does not specify that the method is public, and option B and D are incorrect because they do not describe the method correctly.

Question 14

The JVM periodically performs this process to remove unreferenced objects from memory.
A) memory sweeping
B) garbage collection
C) memory shuffling
D) system restore

Accepted Answer

Garbage collection is the process of automatically freeing memory occupied by objects that are no longer referenced by the program, hence is the correct choice. Memory sweeping and shuffling are not terms commonly used in relation to memory management. System restore has no relevance to memory management in the JVM.

Question 15

Look at the following declaration: enum Tree { OAK, MAPLE, PINE }
What is the fully-qualified name of the PINE enum constant?
A) PINE
B) enum.PINE
C) Tree.PINE
D) Tree(PINE)
E) PINE.Tree

Accepted Answer

The fully-qualified name of an enum constant in Java is .. In this case, the enum name is Tree and the constant name is PINE, so the fully-qualified name is Tree.PINE.

Question 16

You cannot use the fully-qualified name of an enum constant for this.
A) a switch expression
B) an argument to a method
C) a case expression
D) all of these

Accepted Answer

The fully-qualified name of an enum constant cannot be used in a case expression. However, it can still be used as an argument to a method or in a switch expression.

Question 17

What will be returned from a method, if the following is the method header?
Public Rectangle getRectangle()
A) An object of the class Rectangle
B) The address of an object of the class Rectangle
C) The values stored in the data members of the Rectangle object the method changed
D) A graph of a rectangle

Accepted Answer

The answer of What will be returned from a method,...

Question 18

CRC stands for:
A) Code, Reuse, Constancy
B) Class, Responsibilities, Collaborations
C) Class, Redundancy, Collections
D) Class, Recyclability, Collaborations

Accepted Answer

CRC (Class-Responsibility-Collaboration) is a technique used in object-oriented design to help identify and organize the responsibilities of different classes in a system. A CRC model consists of a set of index cards, each representing a class in the system. The class card is divided into three sections: one for listing the class's responsibilities, another for listing other classes with which it collaborates, and a third for notes and references. Code, Reuse, Constancy and Class, Redundancy, Collections are not correct definitions for CRC. Class, Recyclability, Collaborations is not a correct expansion of the CRC acronym.

Question 19

Assume the class BankAccount has been created, and the following statement correctly creates an instance of the class: BankAccount account = new BankAccount(5000.0);
What is TRUE about the following statement?
System.out.println(account);
A) The method will display unreadable binary data on the screen.
B) A compiler error will occur.
C) The account object's toString method will be implicitly called.
D) A runtime error will occur.

Accepted Answer

When the statement System.out.println(account) is executed, the account object's toString method will be implicitly called. This is because every object in Java inherits from the Object class, which contains a default toString method that returns a string that consists of the object's class name and an ID. However, the BankAccount class can override this method to provide a more meaningful string representation of the object.

Question 20

When the this variable is used to call a constructor:
A) it must be the first statement in the constructor making the call
B) it must be the last statement in the constructor making the call
C) it can be anywhere in the constructor making the call
D) you cannot use the this variable in a constructor call

Accepted Answer

The this variable must be the first statement in the constructor making the call, as it is used to call the constructor of the current class. This means that any other statements in the constructor would need to come after the constructor call.

Quiz 8: A Second Look at Classes and Objects

An instance of a class does not have to exist in order for values to be stored in a class's static fields.

The whole-part relationship created by object aggregation is more often called:

If you write a toString method to display the contents of an object, object1, for a class, Class1, then the following two statements are equivalent: System.out.println(object1); System.out.println(object1.toString());

A single copy of a class's static field is shared by all instances of the class.

Look at the following declaration: enum Tree { OAK, MAPLE, PINE } What is the ordinal value of the MAPLE enum constant?

Enumerated types have this method, which returns the position of an enum constant in the declaration list.

If you attempt to perform an operation with a null reference variable:

A declaration for an enumerated type begins with this key word.

The this key word is the name of a reference variable that is available to all static methods.

Assuming the following declaration exists: enum Tree { OAK, MAPLE, PINE } What will the following code display? System.out.println(Tree.OAK) ;

Both instance fields and instance methods are associated with a specific instance of a class, and they cannot be used until an instance of the class is created.

When an object is passed as an argument, it is actually a reference to the object that is passed.

If the following is from the method section of a UML diagram, which of the following statements is TRUE? + add(object2:Stock) : Stock

The JVM periodically performs this process to remove unreferenced objects from memory.

Look at the following declaration: enum Tree { OAK, MAPLE, PINE } What is the fully-qualified name of the PINE enum constant?

You cannot use the fully-qualified name of an enum constant for this.

What will be returned from a method, if the following is the method header? Public Rectangle getRectangle()

CRC stands for:

Assume the class BankAccount has been created, and the following statement correctly creates an instance of the class: BankAccount account = new BankAccount(5000.0) ; What is TRUE about the following statement? System.out.println(account) ;

When the this variable is used to call a constructor: