Week 13 - Exception event FPL

Question 1

What are exceptions?

Answer 1

Exceptions are objects of classes

Question 2

What are the two predefined subclasses of the Throwable class?

Answer 2

Error and Exception.

Question 2

When are Error exceptions thrown?

Answer 2

Error exceptions are thrown by the runtime system for events such as heap overflow and are never handled by user programs.

Question 3

What are user-defined exceptions typically subclasses of?

Answer 3

User-defined exceptions are typically subclasses of the Exception class.

Question 3

What happens if no handler is found in the try construct?

Answer 3

If no handler is found in the try construct, the search continues in the nearest enclosing try construct. If no handler is found in the method, the exception is propagated to the method’s caller, and if no handler is found all the way to main, the program is terminated.

Question 3

What are unchecked exceptions?

Answer 3

Unchecked exceptions are those of class Error and RuntimeException and all their descendants. They are not checked by the compiler.

Question 4

How is binding exceptions to handlers simpler compared to C++?

Answer 4

Binding an exception to a handler is simpler because an exception is bound to the first handler with a parameter of the same class as the thrown object or an ancestor of it.

Question 4

How are exceptions thrown?

Answer 4

Exceptions are thrown using the throw statement, often combined with the new operator to create the exception object.

Question 5

What is the purpose of the finally clause?

Answer 5

The finally clause is used to specify code that is executed regardless of whether an exception is thrown in the try construct.

Question 6

What must be done with checked exceptions?

Answer 6

Checked exceptions that may be thrown by a method must be either listed in the method’s throws clause or handled within the method.

Question 6

Name two predefined subclasses of the Exception class.

Answer 6

IOException and RuntimeException are two predefined subclasses of the Exception class.

Question 7

Can a method declare more exceptions in its throws clause than the method it overrides?

Answer 7

No

Question 8

What are the three alternatives for dealing with an exception listed in a called method’s throws clause?

Answer 8

1) Catch and handle the exception
2) Catch the exception and throw an exception listed in its own throws clause
3) Declare the exception in its throws clause and do not handle it.

Question 9

What happens when an assert statement evaluates to false?

Answer 9

When an assert statement evaluates to false, an AssertionError exception is thrown.

Question 10

What is a key advantage of the throws clause compared to C++?

Answer 10

The throws clause provides more information to the programmer by specifying which exceptions a method can throw, unlike the throw clause in C++ which says little.

Question 11

What is the purpose of the else block in the try-except construct?

Answer 11

The else block in the try-except construct is executed if no exceptions are raised in the try block.

Question 11

What does the assert statement do?

Answer 11

The assert statement tests a Boolean expression and raises an AssertionError with an optional message if the expression evaluates to false.

Question 11

How are exception handlers written?

Answer 11

Exception handlers are written using the try-except structure, where each except block specifies the type of exception it handles.

Question 12

How are exceptions raised in another language?

Answer 12

Exceptions are raised using the raise statement, which can include an error message.

Question 13

Where are exception handlers placed in another language?

Answer 13

Exception handlers are placed at the end of a begin block and are introduced by the rescue keyword.

Question 14

What unique feature does another language have for handling exceptions that allows code to be rerun?

Answer 14

Another language has a retry statement at the end of a handler that allows the code that raised an exception to be rerun.

Question 15

What is an event in the context of event handling?

Answer 15

An event is a notification that something specific has occurred, such as a mouse click on a graphical button.

Question 16

What is an event handler?

Answer 16

An event handler is a segment of code that is executed in response to an event.

Question 17

What is the purpose of the GUI component library?

Answer 17

The GUI component library provides a collection of classes and interfaces for creating GUI components, such as text boxes and radio buttons.

Question 18

What connects events to event handlers?

Answer 18

Event listeners connect events to event handlers.

Question 18

What creates events in user interactions with GUI components?

Answer 18

User interactions with GUI components create events.

Question 19

How does an event generator inform a listener about an event?

Answer 19

An event generator tells a listener of an event by sending a message.

Question 20

How are event generators and listeners connected?

Answer 20

Event generators and listeners are connected by event listener registration.

Question 21

What is the role of an interface in event handling?

Answer 21

An interface is used to make event handling methods conform to a standard protocol.

Question 22

What must a class that implements a listener also implement?

Answer 22

A class that implements a listener must implement an interface for the listener.

Question 23

What user actions are associated with ItemEvent?

Answer 23

ItemEvent is associated with the event of clicking a checkbox, a radio button, or a list item.

Question 24

What must be done to handle ItemEvent events?

Answer 24

The handler for ItemEvent events should be implemented, and the listener must be registered.

Question 25

Can each event handler receive parameters?

Answer 25

Yes

Question 26

What class does RadioB extend, and what interface does it implement?

Answer 26

RadioB extends JPanel and implements ItemListener.

Question 27

What does the itemStateChanged method do?

Answer 27

The itemStateChanged method determines which button is selected and sets the font accordingly.

Question 28

What are the two approaches to event handling in .NET?

Answer 28

The two approaches in .NET are Windows Forms and Windows Presentation Foundation.

Question 29

How is a GUI constructed in Windows Forms?

Answer 29

A GUI is constructed using System.Windows.Forms, which implicitly provides a window without the need to build a frame or panel explicitly.

Question 30

How is a radio button’s state tested in C#?

Answer 30

A radio button’s state is tested with the Boolean Checked property.

Question 30

How are components positioned in Windows Forms?

Answer 30

Components are positioned by assigning a new Point object to the Location property of the component.

Question 31

List some widgets available in tkinter.

Answer 31

Some widgets include Button, Canvas, Checkbutton, Entry, Frame, Label, Listbox, Menu, Menubutton, Message, Radiobutton, Scale, Scrollbar, Text, Toplevel, LabelFrame, and PanedWindow.

Question 32

What are some event handler bindings in tkinter?

Answer 32

Event handler bindings include <Button-1>, <B1-Motion>, <ButtonRelease-1>, <Double-Button-1>, <Enter>, <Leave>, <FocusIn>, <FocusOut>, <Return>, <Key>, <Shift-Up>, and <Configure>.</Configure></Shift-Up></Key></Return></FocusOut></FocusIn></Leave></Enter></Double-Button-1></ButtonRelease-1></B1-Motion></Button-1>

Question 33

What additional clause does Java include in its exception handling?

Answer 33

Java includes a finally clause in its exception handling.

Question 34

What is the primary concern of imperative languages?

Answer 34

The primary concern of imperative languages is efficiency rather than suitability for software development.

Question 35

What is an event in programming?

Answer 35

An event is a notification that something has occurred that requires handling by an event handler.

Question 35

What is a lambda expression?

Answer 35

A lambda expression specifies parameter(s) and mapping functions, such as λ(x) x * x * x.

Question 36

Describe functional composition.

Answer 36

Functional composition is a functional form that takes two functions as parameters and yields a function whose value is the first actual parameter function applied to the application of the second, e.g., h(x) ≡ f(g(x)). (exp: f(x) ≡ x + 2 and g(x) ≡ 3x, h ≡ f ̊ g yields (3x) + 2.)

Question 36

What is the apply-to-all functional form?

Answer 36

The apply-to-all functional form takes a single function as a parameter and yields a list of values obtained by applying the given function to each element of a list of parameters. (exp: h(x) ≡ x * x, α(h, (2, 3, 4)) yields (4, 9, 16).)

Question 36

Why is it challenging to manage the state changes in large imperative programs?

Answer 36

Managing the state changes in large imperative programs is a daunting task due to the importance of variables and how the program’s state changes.

Question 37

What is a higher-order function or functional form?

Answer 37

A higher-order function or functional form takes functions as parameters and yields a function as its result or does both.

Question 38

What is referential transparency in FPLs?

Answer 38

Referential transparency means the evaluation of a function always produces the same result given the same parameters, making the semantics of FPLs simpler than imperative languages.

Question 39

What are primitive functions in FPLs?

Answer 39

Primitive functions are a set of basic functions provided in FPLs, with a smaller number being considered beneficial.