CPSC 2150 Exam 1

What should be included in a user story?

The role of the user, the action the user will take in the system, and the benefit to the user

Can the system itself be in a user story?

No

Which of the following are examples of non-functional requirements?

A. The system should run on Unix
B. The system must be written in Java
C. The user is able to view the status of their order
D. As a customer, I can place an order on the website, so I can place an order without having to call the store

A. The system should run on Unix
B. The system must be written in Java

What are the three parts of a UML class diagram?

The name, attributes, and methods of a class

(T/F) If you are creating a UML class diagram for a person, and that person will have multiple phone numbers, the data type of the "PhoneNumber" attribute should be a list or an array.

False

Which symbol is used to show that a method or attribute is private?

"-"

Which symbol is used to show that an attribute or method is package visible?

"~"

Which symbol is used to show that an attribute or method is public?

"+"

(T/F) In a UML Activity diagram, an "Activity" can be something that would take multiple lines of code to write, as long as it does not require and decisions

True

(T/F) In a UML Activity Diagram, an "Activity" cannot be a call to another function

False

(T/F) In a UML Activity Diagram, the text inside of an "Activity" or a "Decision" has to be written in code.

False

(T/F) In a UML Activity Diagram, a "Decision" may have multiple paths leaving it.

True

(T/F) Drawing UML diagrams is an important part of our design process.

True

Who is responsible for making sure the precondition of a method is true?

The implementer of the client code that calls the method

Who is responsible for making sure the postcondition of a method is true

The implementer of the method

At which times is it safe to assume that the invariants are true?

After the constructor of the class has completed, at the very beginning of a public method, and right after a public method has finished

(T/F) It is a best practice to have an if statement at the beginning of each method implementation to check that the preconditions are true

False

Every single class in Java extends the \___________________________ class

Object

If you do not override the toString method in a class that you create, what will happen when you call toString on an object of that class?

A string showing the memory address will be returned

What Java operator will tell us whether or not an object's data type is a certain class

instanceOf

Packages in Java allow us to have...

A. An array with different datatypes in it
B. A logical structure and grouping of classes
C. An opportunity to reuse the names of a class since it will be in a distinct package
D. Another layer of encapsulation by encapsulating classes together

B. A logical structure and grouping of classes
C. An opportunity to reuse the names of a class since it will be in a distinct package
D. Another layer of encapsulation by encapsulating classes together

(T/F) A class can be in multiple packages.

False

In Java, if you do not specify a visibility level for a class, the visibility level will be \________________________________

package

A static member belongs to the \______

class

(T/F) You can call a static member of a class without creating an instance of that class, by calling it directly from the class name.

True

If you have a reference type variable called foo that is declared final, which of the following cannot change?

A. The memory location that foo is pointing to
B. The abstract values stored inside of foo

A. The memory location that foo is pointing to

Which of the following can be the declared type in the Java programming language (as allowed by the compiler, not following any best practices we discussed).

A. Interfaces
B. Classes

A. Interfaces
B. Classes

Which of the following can be the dynamic type in the Java programming language (as allowed by the compiler)

A. Interfaces
B. Classes

B. Classes

Which of the following can be in an interface file?

A. private abstract methods
B. public abstract methods
C. public static final data variables
D. Private data variables
E. A constructor
F. Any type of public method
G. Any type of private method

B. public abstract methods
C. public static final data variables

(T/F) When determining whether or not you can call a method for an object in your code, the Java compiler will check to see if that method exists in the DYNAMIC type of the object

False

(T/F) Java requires that the DECLARED type of a variable must be the exact same as the DYNAMIC type of a variable

False

(T/F) A class can be the DYNAMIC type of a variable that has an interface as the DECLARED type if the class implements that interface.

True

What is "Coding to the Interface?" Note: the best practice, not the general idea of using interfaces.

Coding to the Interface is when you have all of your declared data types be interface data types, thus requiring your code to be written using only the methods provided by the interface and not specific to any implementation of the interface.

What is one benefit of following the best practice of "Coding to the Interface?"

You can change the implementation in your interface without affecting the client code.

Since your code is specifically written for the interface and not for any implementation, you can later change which implementation is used just by swapping out the constructor call that sets the dynamic type of the variable. Additionally any function that takes in a parameter will be taking in the interface type, and not the specific implementation type, which means any implementation can be passed in as the parameter for the method.

\_________________________ is ensuring that every object has its own role

Separation of concerns

\__________________________ is controlling access to data and operations

Information hiding

\__________________________ is grouping related data and operations together in one object

Encapsulation

(T/F) The precondition automatically checks and enforces itself by checking the value of the parameter and returning an error is the parameter is incorrect.

False

Who is responsible for making sure that the precondition for a function is met?

The client who calls the function

Who is responsible for making sure that the postcondition for a function is met

The implementer who codes the function

(T/F) It Is good practice to use an if statement to inside the method to check to see if the precondition is met

False (it's the client's job)

Which of the following is not a time when we would assume the invariant to be true?

A. After the constructor has finished
B. At the beginning of a public method
C. After a public method has finished
D. During the body of the public method or constructor

D. During the body of the public method of constructor (during execution)

Who is responsible for making sure a class invariant is true?

The implementers of the class and its public methods

It is a good idea to make data fields of a class public to make access to them easier and avoiding coding unnecessary getter and setter functions

False

Which is the best design practice?

A. Provide getter and setter functions to allow access to data members
B. Make data member public for direct access
C. Provide public member functions for controlling and observing abstract values of the objects, not just getting and setting.

C. Provide public member functions for controlling and observing abstract values of the objects, not just getting and setting.

What contains the actual code for a method?

A. The interface
B. The class that implements the interface

B. The class that implements the interface

What contains the private attributes?

A. The interface
B. The class that implements the interface

B. The class that implements the interface

In java, the declared type can be:

A. Only an interface
B. Only a class
C. Either an interface or a class

C. Either an interface or a class

In Java the dynamic type can be?
A. Only an interface
B. Only a class
C. Either an interface or a class

B. Only a class

(T/F) Our interface specification and the contracts in the interface can refer to private data variables.

False

A \________ can implement a \__________.

Class, interface
Abstract class, interface

(T/F) Java 8 and later allows private data fields in the interface.

False

Java 8 and later allows code in our interface as long as it is a \___________ method.

default

A \_____ operation needs access to the private data of a class.

Primary

A \_____ operation can be implemented by calling other existing operations.

Secondary

A \______ can extend a \___________.

Class, class
Interface, interface

When java is determining which version of an overridden method to run, how will it make that decision?

It will use the method in the dynamic type.

(T/F) An abstract class can only have data fields that are static.

False

(T/F) An abstract class can contain methods with bodies (code)

True

What is an example of a generic type you have already used?

List

(T/F) In order to pass a data TYPE in for the parameterized data type of a generic class, then the TYPE must be an immutable data type.

False

(T/F) In order to pass a data TYPE in for the parameterized data type of a generic class, then the TYPE must be an immutable data type.

True

Why do we hide information?
A. To keep data in sync
B. To keep data accurate
C. To keep data secure
D. To not overwhelm other programmers with implementation details

All of the above!

A good design helps with...

Reuse, debugging, and adapting to change

What are the two roles in a contract?

Implementer & client

A \_______________ (aka a requires clause) defines the client's responsibility., defines what the client must do before calling the code, can be related to the parameters, and can be the current state of the object

precondition

Why use preconditions?

Efficiency!

In the absence of preconditions, implementations will have to do error checking.

Consider an operation (or method) to perform a binary search to determine if an item is in an array.

What is the precondition?

The array must be sorted.

Consider an operation (or method) to perform a binary search to determine if an item is in an array.

What if the function checked the precondition on its own?

It would take linear time to check that the array is sorted, though it takes only log time to search, defeating the entire purpose of an efficient search!

Does an integer division operation have a precondition?

Yes! The divisor should not be 0.

A \______________ (aka an ensures clause) characterizes the implementer's responsibility (aka, your code).

postcondition

What do postconditions tell the client?

Tells the client what the code does (return values, events, state of the object)

Contracts are \____________, not actual code.

comments

Preconditions and Postconditions were about things that are true \________________ some method call or event

before AND after

The invariant may not be true when?

During the execution of a method
Before the call of a private method
After the call of a private method

(T/F) The implementer of any public class method is responsible for ensuring that the invariant is always true.

True

Who is responsible for the Invariant?

The implementer of the class defines the invariant

What are the two kinds of members in a class declaration?

Fields, ie data (determine the state)
and Methods, ie procedures (access/modify the state)

(T/F) Private members can be accessed only by instances of same class

True

(T/F) Private members provide concrete implementation / representation

True

(T/F) Public members can be accessed by any object

True

(T/F) Public members provide abstract view (client-side)

True

Who is the audience meant for preconditions and postconditions?

Preconditions and postconditions are meant for the client of the class (aka other software engineers)

Who are the invariants meant for?

the implementer

What is an interface?

Where interactions occur; describes what classes do, not how they should do it

The interface itself is \____ or \_____ visible.

public or package

What must the fields/attributes of an interface be declared as?

public static final (ie constants)

Cannot contain private fields/attributes

What must the methods of an interface be declared as?

public abstract

Cannot be final

(T/F) Class can declare more methods than required by interface

True

(T/F) Class can implement more than one interface

True

What is the difference between a declared type and a dynamic type (what time will they be declared)?

Declared type: set at compile time (by declaration), and a dynamic type: set at run time (by new)

(T/F) Compiler can infer dynamic type.

False

(T/F) Operator instanceOf tests the run-time type.

True

(T/F) Interfaces can be used as dynamic types.

False! Interfaces can only be used as declared types.

All dynamic types are \__________

classes

All runtime objects are constructed from a \_________, not a \________.

class, not an interface

\_____________________ allow us to tie the concepts specified in the interface to the private data in the implementation (ie our class)

Correspondences

Correspondences tie the \______________ to the \_______________.

Abstraction to the implementation

The implements relation may hold between a \___________ and a \___________.

Class and an interface

Java now allows code in our interface file as long as it is a \______or \_________ method

default or static