Exam Preparation Elliot

Question 1

Benefits of AWT

Answer 1

Good for background system specific code

Question 2

Benefits of Swing

Answer 2

Lightweight, pure java, subclass of AWT Frame

Question 3

What is a JOptionPane

Answer 3

Popup box with Y, N, and Cancel

Question 4

What is the general structure of. JMenuBar

Answer 4

JMenuBar(JMenu(JMenuItem))

Question 5

Was is JFrame a subclass of, and what is it not a component of

Answer 5

AWT.frame, JFrame is not a Component

Question 6

What is a general overview of MVC

Answer 6

View passes input to Controller, Controller updates the View

Controller changes the state of the Model

ModelChanged by the Model updates the values in the view

Question 7

What parts are in the event dispatch thread

Answer 7

Event Queue, Event Loop, Event handler (click > data received > refresh the gui), GUI components

Question 8

What part is in the helper thread and where does it send its data

Answer 8

Long task processing, this will add to the event queue

Question 9

What is an event source

Answer 9

A component generating an event (“fires”)

Question 10

What is an event

Answer 10

A user interaction

Question 11

What is an eventListener

Answer 11

An object implementing a handler to react to an complete a task (listeners need to be registered to a source)

Question 12

What is the general form of a listener

Answer 12

JObject created
name.addActionListener(new actionListener() {
override ActionPerformed(actionEvent e) {
name.method();
}
});
add the object to the panel

Question 13

What is the mouse listener called

Answer 13

MouseMotionListener

Question 14

What is the difference between Adaptors and Listeners

Answer 14

Listeners are interfaces, Adaptors are abstract classes

Adaptors only require implementation of the required events

Question 15

What is the general form of an adaptor

Answer 15

panel.add(new MouseAdaptor() {
    override the MouseMoved(MouseEvent arg0) {
        doStuff...
    }
});

Question 16

What does the Event dispatch thread do

Answer 16

Executes GUI code

Question 17

What are the three reasons to have the Event dispatch thread

Answer 17

Responsive, long computations won’t lock up the GUI

ThreadSafe, only the EDT can access the GUI

Swing can use SwingWorker to deal with computational tasks

Question 18

How to use SwingUtilities, what will this ensure

Answer 18

Use invokeLater on runnable as a parameter to start the GUI, this will ensure GUI is on the EDT

Question 19

What is the general form of SwingUtilities

Answer 19

SwingUtilities.invokeLater(new Runnable() {
    public void run() {}
});

Question 20

What is the general form of SwingWorker

Answer 20

SwingWorker worker = new SW() {
    override doInBackground()

Question 21

What are the four main regex methods

Answer 21

compareTo(), substring(), indexOf(), matches()

Question 22

How does compareTo() function

Answer 22

• if value alphabetically before, + if alphabetically behind, 0 is match

Question 23

File I/O text

Answer 23

Format with Formatter(format), BufferedWriter

Scan with Scanner and scanner methods hasNext(), nextLine(), next(), BufferedReader

Question 24

Binary file I/O class and methods

Answer 24

DataInput/OutputStream; read/write Byte, Int, Double

Question 25

Steps to be able to serialize

Answer 25

Class has to implement Serializable
Wrap non serialisable by overriding read/writeObject
Unserializable fields will need to catch IOExc

Question 26

Why use threads

Answer 26

Efficient, responsive, allows for task separation

Question 27

Compare processes and threads

Answer 27

Processes spawn threads, have a call stack, PC, and their own memory

Threads have a class stack and a PC and share the memory of their parent process

Question 28

Why can threads be faster

Answer 28

Threads can be separated onto multicore systems

Question 29

What are the six main thread states

Answer 29

waiting
timed
waiting
blocked
terminated
ready
running

Question 30

What does the OS control in regards to threads

Answer 30

Switching between ready and running

Question 31

Thread waiting methods

Answer 31

wait(), notifyAll(), sleep()

Question 32

Thread Blocking methods

Answer 32

enter/exitSync()

Question 33

Compare threads and runnable

Answer 33

Both need a run() method

Extend thread, implement runnable

You can extend another class with runnable

Runnable has a lower overhead due to a single runnable instance

Question 34

What are Daemon threads

Answer 34

Service, background threads, will auto terminate once main has terminated

Question 35

What is ExecutorService

Answer 35

A means of reusing threads

Question 36

What are the types of thread pools

Answer 36

newFixedThreadPool(int), newCachedThreadPool()

Question 37

What are the main ExecutorService methods

Answer 37

execute(runnable)

shutdown(), orderly kill sequence

shutdownNow(), kill and halt, return a list of shutdown threads, no guarantees

awaitTermination(), block invocation until everything is complete

Question 38

What does synchronised do

Answer 38

Creates a lock on method declaration, only one tread can access the method at one time (Instance monitor lock) note that unsynchronised methods with be accessible

Question 39

How can we avoid producer/consumer issues

Answer 39

Use synchronised and implement checks before allowing method/value access

Question 40

What is the BlockingQueue

Answer 40

It is an array(int) which stores pending operations

Question 41

What are the main BlockingQueue methods

Answer 41

add (illegalStateExc)
put (will wait if no space in queue)
remove (returns the head, NoSuchElementExc)
poll (return the head)

note BlockingQueue ignores FIFO

Question 42

What is Callable and what does its method return

Answer 42

An interface with a single call() method returning the result of a threads task, an exception if task incomplete

Question 43

What is the general format of Callable

Answer 43

public class SimpleCall implements Callable {
    override String call() throws Exception {
        return String datarow = "A bunch of values";
    }
} // Asynchronous result

Question 44

What is the Future object

Answer 44

Obj represents a result of an asynchronous computation

Question 45

What are the main Future methods

Answer 45

cancel(boolean interrupt) throws InterruptedException

isCancelled() return true of task sent and interruptedException

isDone() return true if task is complete

get(optional timeout) wait for completion and return result

Question 46

What are the Future exceptions

Answer 46

Cancellation, computation canceled

Execution, computation threw an exc

Interrupted, thread interrupted while waiting

Question 47

How to use FutureTask

Answer 47

Implement the future interface

call the get method of callable