Question 1

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) A runtime error will occur.
B) The method will display unreadable binary data on the screen.
C) The account object's toString method will be implicitly called.
D) A compiler error will occur.

Accepted Answer

The statement System.out.println(account); will call the account object's toString method, which is implicitly called when an object is printed using the println method. If the toString method has not been explicitly defined in the BankAccount class, the default toString method from the Object class will be used, which displays the class name and the memory address of the object.

Question 2

Of the following, which would be considered the no-arg constructor for the Rectangle class?
A) public Rectangle(int len, int width)
B) public Rectangle(double len, double width)
C) public Rectangle()
D) All of the above

Accepted Answer

A no-arg constructor is a constructor that takes no parameters. The only constructor that fits this description is option C. Options A and B take two parameters, and are therefore not no-arg constructors.

Question 3

If you have defined a class SavingsAccount with a public static method getNumberOfAccounts, and created a SavingsAccount object referenced by the variable account20, which of the following will call the getNumberOfAccounts method?
A) account20.getNumberOfAccounts();
B) SavingsAccount.getNumberOfAccounts();
C) getNumberOfAccounts();
D) None of the above

Accepted Answer

Since getNumberOfAccounts is a public static method of SavingsAccount class, it can be called directly using the class name followed by dot operator and method name, i.e. SavingsAccount.getNumberOfAccounts(). Option A is incorrect because getNumberOfAccounts is a static method and cannot be called using an instance of the class. Option C is incorrect because there is no reference to the class name, so it would not know which class's getNumberOfAccounts method to call. Option D is incorrect because at least option B will call the method.

Question 4

Overloading is
A) writing a method that does too much processing.
B) writing a program that is too large to fit in memory.
C) having two or more methods with the same name, but different signatures.
D) having two or more methods with the same signature.

Accepted Answer

Overloading refers to having two or more methods or constructors within the same class with the same name, but different parameters or signatures. This allows for more flexibility and convenience, as different versions of the same method can be used for different purposes, without having to come up with different method names.

Question 5

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 can be anywhere in the constructor making the call.
C) it must be the last statement in the constructor making the call.
D) You cannot use the this variable in a constructor call.

Accepted Answer

The this variable must be used as the first statement in a constructor making a call to another constructor. This is done to ensure that the object is properly initialized before the new constructor starts executing.

Question 6

Assuming the following declaration exists:
Enum Tree { OAK, MAPLE, PINE }
What will the following code display?
System.out.println(Tree.OAK);
A) OAK
B) Tree.OAK
C) 0
D) 1

Accepted Answer

The code will display the name of the enum constant "OAK", which is the value assigned to the constant.

Question 7

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

Accepted Answer

The method that enumerations have which returns the position of an enum constant in the declaration list is called "ordinal". Therefore, the correct choice is C, "ordinal".

Question 8

The "has a" relationship is sometimes called a(n) ________ because one object is part of a greater whole.
A) enterprise
B) possession
C) mutual relationship
D) whole-part relationship

Accepted Answer

The "has a" relationship is a whole-part relationship because one object is a part of a greater whole.

Question 9

By default, a reference variable that is an instance field is initialized to the value
A) null.
B) 0.
C) void.
D) static.

Accepted Answer

By default, a reference variable that is an instance field is initialized to null. This means that the reference variable does not refer to any object in memory.

Question 10

A method's signature consists of
A) the method name and the parameter list.
B) the return type, the method name, and the parameter list.
C) the size of the method in memory.
D) the return type and the method name.

Accepted Answer

The method signature in many programming languages, including Java, consists of the method name and the parameter list (types and order of parameters), but does not include the return type.

Question 11

When you write an enumerated type declaration, you
A) are actually creating a special kind of class.
B) do not enclose the enum constants in quotation marks.
C) should use the standard convention of writing the enum constants in uppercase.
D) All of the above

Accepted Answer

A) Enumerated types in Java are actually their own data type, but they do not require you to create a new class.
B) Enum constants should not be enclosed in quotation marks, as they are not Strings.
C) It is a standard convention to write enum constants in all uppercase to distinguish them from other variables and constants within a program.

Question 12

A class that is defined inside of another class is called a(n)
A) nested class.
B) enumerated class.
C) inner class.
D) helper class.

Accepted Answer

A class that is defined inside of another class is called an inner class. It is also known as a nested class, but of the given options, inner class is the most commonly used term. Enumerated classes are a specific type of class used for creating enumerated types in Java. Helper classes are classes that assist in the implementation of other classes but are not defined inside them.

Question 13

You cannot use the fully-qualified name of an enum constant for
A) a case expression.
B) an argument to a method.
C) a boolean expression.
D) All of the above.

Accepted Answer

Enum constants are implicitly static final and can be referred using unqualified names. Therefore, using the fully-qualified name of an enum constant for a case expression is unnecessary and also not allowed by the compiler.

Question 14

If the following is from the method section of a UML diagram, which of the following statements is true?
+ equals(object2:Stock) : boolean
A) This is a public method that accepts a Stock object as its argument and returns a boolean value.
B) This is a public method that returns a reference to a String object.
C) This is a private method that receives two objects from the Stock class and returns a boolean value.
D) This is a private method that returns a boolean value.

Accepted Answer

The method name "equals" suggests that it is used for object comparison. The parameter is of type Stock which means it accepts a Stock object argument. The return type of the method is boolean, which implies that the method returns true or false to indicate whether the two Stock objects are equal or not. The fact that it is not specified as private implies that it is a public method accessible from other classes.

Question 15

When you make a copy of the aggregate object and of the objects it references,
A) you are performing a shallow copy.
B) you are performing a nested copy.
C) you are performing a deep copy.
D) a compiler error will occur.

Accepted Answer

When you make a copy of the aggregate object and of the objects it references, you are performing a deep copy. This means that you are creating a completely separate copy of the original object and all its referenced objects, rather than just copying over the references themselves.

Question 16

________ is the term for the relationship created by object aggregation.
A) "Has a"
B) Inner class
C) "Is a"
D) One-to-many

Accepted Answer

The term for the relationship created by object aggregation is "has a". Aggregation is a process of combining multiple objects to create a new object that can be used as a single unit. In this relationship, an object 'has a' relationship with the other object.

Question 17

If object1 and object2 are objects of the same class, to make object2 a copy of object1
A) write a method for the class that will make a field by field copy of object1 data members into object2 data members.
B) use the copy method that is a part of the Java API.
C) use the default constructor to create object2 with object1 data members.
D) use an assignment statement to make object2 a copy of object1.

Accepted Answer

A field-by-field copy method explicitly defined in the class allows for a controlled and accurate duplication of an object's state from one instance (object1) to another (object2). Java does not provide a universal copy method in its API for object duplication, and the default constructor or assignment statement alone may not achieve a deep copy if the object contains complex data structures or references.

Question 18

When a method in the ________ class returns a reference to a field object, it should return a reference to a copy of the field object to prevent "security holes."
A) aggregate
B) inner
C) String
D) nested

Accepted Answer

When working with aggregate classes, returning a reference to the original field object can create security holes as the calling method can potentially modify the original object. Therefore, it is best practice to return a copy of the field object to prevent this.

Question 19

The only limitation that static methods have is
A) they must be declared outside of the class.
B) they cannot refer to nonstatic members of the class.
C) they can only be called from static members of the class.
D) they can refer to only nonstatic members of the class.

Accepted Answer

Static methods cannot refer to nonstatic members of the class because nonstatic members belong to a specific instance of the class, and static methods do not have access to any instance-specific data. Static methods can, however, be declared and called from within the class.

Question 20

When a method's return type is an object, what is actually returned to the calling program?
A) a reference to an object of that class
B) only the values in the object that the method accessed
C) an object of that class
D) a null reference

Accepted Answer

When a method's return type is an object, a reference to an object of that class is returned to the calling program. This reference points to the object in memory and allows the calling program to access and manipulate its properties and methods.

Quiz 6: A Second Look at Classes and Objects

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) ;

Of the following, which would be considered the no-arg constructor for the Rectangle class?

If you have defined a class SavingsAccount with a public static method getNumberOfAccounts, and created a SavingsAccount object referenced by the variable account20, which of the following will call the getNumberOfAccounts method?

Overloading is

When the this variable is used to call a constructor

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

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

The "has a" relationship is sometimes called a(n) ________ because one object is part of a greater whole.

By default, a reference variable that is an instance field is initialized to the value

A method's signature consists of

When you write an enumerated type declaration, you

A class that is defined inside of another class is called a(n)

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

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

When you make a copy of the aggregate object and of the objects it references,

________ is the term for the relationship created by object aggregation.

If object1 and object2 are objects of the same class, to make object2 a copy of object1

When a method in the ________ class returns a reference to a field object, it should return a reference to a copy of the field object to prevent "security holes."

The only limitation that static methods have is

When a method's return type is an object, what is actually returned to the calling program?