Cs 180

Front 1

Is java case sensetive?

Does java ignore overflow and underflow?

Back 1

- Java is case sensetive

- java does ignore underflow and over flow

( this means that an integer incremented at maximum value will loop back to minimum value)

Front 2

What does the declaration of a variable do?

Back 2

- arranges for space to be allocated for the variable

- ensures only valid operators can be performed on this variable

Front 3

What is the difference (syntactically) between declaring a variable and initializing a variable?

Back 3

Declaration:

int cars;

Initialization (first assignment):

int cars = 5;

assignment:

cars = 6;

In java, a variable can only be declared once. (probably within same method)

Front 4

compare strings using...?

Back 4

obj.equals("string");

NOT ==

Front 5

Formula for comparing doubles

Back 5

Front 6

what is the output?

Back 6

"seven"

Front 7

3 things happen with evaluation of this

double cars = new double[250]

Back 7

1. Allocates 250 double precision storage locations

2. variable 'cars' stores the first location

3. initializes each 250 locations to 0.0

Front 8

What is the output?

Back 8

"CS 1234"

alice points to what alicia is pointing to

(which is the first location of the string array alicia)

Front 9

ArrayList jim = new ArrayList();

what is command to add "tom" to array list Jim at first location?

Back 9

jim.add(0,"tom");

Front 10

1. What is a method signature?

2. How does it relate to overloaded methods?

Back 10

1. A method signature is the Method Name, parameter types

NOT method type!

2. to overload methods, must have variance in method signature

Front 11

method parameters are located ...

Back 11

public int print(PARAMETER HERE) {

}

Front 12

arguments are located...

Back 12

main {

Jim j = new Jim(ARGUMENTS HERE) ;

}

Front 13

What is an interface, and why is it used?

Back 13

A interface is like an agreement to implement certain method signatures.

The methods signatures within the interface do not have bodies.

Front 14

Can interfaces be instantiated?

Back 14

location 8780

Front 15

what is an abstract method?

Back 15

used in interfaces

Front 16

What 3 things can an interface NOT have?

Back 16

Cannot have

1. method bodies (use abstract method)

2. fields ( other than constants)

3. static methods (because why would an interface need functional methods?)

Front 17

Fields in interfaces are implicitly declaired..?

Back 17

public, final, & static

they must be declared with an initializer(=)

(methods are implicitly public)

Front 18

If a field in an interface(a constant) is changed, what value will the dependent classes see?

Back 18

the updated value

Front 19

A class can implement how many interfaces? Extend how many parent classes?

Back 19

implement MANY

extend ONE

Front 20

what is a prerequisite to be able to use a for each loop

Back 20

"list" must implement the ITERABLE interface

Front 21

what is a field?

Back 21

an attribute of an OBJECT or THE CLASS

Front 22

what is a method?

Back 22

an operation on an OBJECT or THE CLASS

Front 23

what is static vs non static?

Back 23

static is 'of the class':

(static field) one memory location/value shared by all objects of class

non-static is 'of the/an object'

Front 24

Variables:

what is an instance variable?

class variable?

local variable?

Back 24

instance variable: non-static fields in a class declaration

Class variables: static fields in a class declariation

local variables: variables in a method or block

Front 25

what may only access static fields and call other static methods?

can be called using the class name

Back 25

static methods

Front 26

what is a good rule of thumb for scope of a variable?

scope is visivility (think teleSCOPE)

Back 26

the variable is usable from the point it is declared to the end of the block

Front 27

public void (int x) {
int x = 0;

}

is this legal?

Back 27

nope

Front 28

example of field hiding

Back 28

Front 29

what is "this"

Back 29

reference to current object

Front 30

when does an object of reference type die?

Back 30

when there is nothing pointing to it!

Front 31

what is the output

Back 31

42

-1

the address is sent

- x points to the first location of the array list

- a then points to the first location of the array list

a can then modify the value without.

notice this way you can modify an array without having to have a method return anything

does not work on int, Integer, double, Double..

Front 32

definition of encapsulation and why its important.

Back 32

encapsulation is hiding information and methods that completes a task so that an end user experiences only the final output and does not have to worry about how the computation took place. This is good in team settings when programs get large and chunks of code need to be abstracted to a single line.

Front 33

difference between access modifiers:

public?

private?

protected?

Back 33

public: fields/methods can be accessed from outside the class (NO restriction)

private: fields/methods can NOT be directly accessed from outside the class

protected: seen in class, subclass (even if subclass is in a different package) , same package

Front 34

what is a checked exception

Back 34

- needs to be caught/handled before compilation time

- reminder from compiler to programmer about potential failure state

- subclass of Exception

ex: IOException, DataAccessException

Front 35

What is an Unchecked Exception

Back 35

- not checked at compile time.

- generally programming error

ex: lovely NullPointerException

ArrayIndexOutOfBounds

- subclass of RunTimeException

Front 36

convention for access modifiers

Back 36

field are private, can have getters/setters

methods are public

Front 37

can you have an ArrayList

(of primative types)?

Back 37

no! however, can have ArrayList

Integer being the wrapper class for int

Front 38

.length() is for ?

.lenght is for ?

Back 38

- String.length();

int[] d = new int[3];

- d.length;

Front 39

in sub-class constructor...

Back 39

super is called first, implicitly if not specified

think: the parent must exist before the child, to make the parent, then create child

Front 40

True/False

In one constructor method, you can call both

- super()

and

-this()

Back 40

False!

Front 41

instance of operator

Back 41

all objects are instances of Object

Front 42

what is the call stack?

Back 42

- Each method is a frame.

- Each frame holds storage for parameters and local variables of the method.

Front 43

syntax of a basic try/catch block..

Back 43

- 'Exception' is a class name

this one is just catching the most generic exception which is Exception

Front 44

what does a method do 'syntatically' when it doesnt want to handle the exception, but pass the problem to someone else , like an incompetent *******

Back 44

Front 45

what is needed to write ones own exception?

Back 45

Front 46

what is the trend in catch blocks?

Back 46

specific to general

Front 47

Finally clause....

Back 47

executes no matter what!

Front 48

domain decomposition

Back 48

a way of splitting up tasks with threads in which the same code processes different sub-domains

Front 49

task decomposition

Back 49

a way of splitting up task with threads based on nature of the task

one thread handle graphics in GUI

other thread handle backend code

Front 50

if we have, Thread t;

t.join()

does what?

Back 50

blocks the CURRENT THREAD until thread t completes.

is generally in try/catch

for InterruptedException

Front 51

Back 51

important that threads synchronize on same object

example , if threads are of one class

have a class variable,

private static Object gatekeeper = new Object();

Front 52

thread state map

Back 52

Front 53

importance of buffering

Back 53

decreases amount of read calls necessary.

reads 'more than needed'

important to flush buffers!

Front 54

FileOutputStream

Back 54

low level I/O

handles: raw data, byte-oriented

Front 55

DataOutputStream

Back 55

High level I/O

handles: java primitive types

Front 56

ObjectOutputStream

Back 56

Object I/O

handles: java objects

Front 57

DataOutputStream

and

ObjectOutputStream

need to build off?

Back 57

- FileOutputStream takes file as arguement

- Data/Object output takes FileOutput obj as arguement

Front 58

. class is compiled version of .java

Back 58

.class in not human readable

.java is

Front 59

read/write from a text file

Back 59

read:

BufferedReader r = new BufferedReader(new FileReader(file object));

write:

PrintWriter w = new PrintWriter(new FileOutputStream( new File ("filename")));

Front 60

Internet Protocol

Back 60

128.10.2.21

identifies host

a computer

Front 61

Domain Name System

Back 61

maps

128.10.9.143

to

data.cs.purdue.edu

Front 62

Transmission Control Protocol

Back 62

identifies ports on hosts for a network connection

Front 63

Socket

Back 63

Ip address + TCP port

house + streetname

Front 64

how many sockets make a connection?

Back 64

2

Front 65

Servers wait for connection

Back 65

One physical device can be both server and client, at different times

Front 66

ServerSocket has .accept() method that waits

accept returns a Socket object

Back 66

kool

Front 67

to implement server with many client connection. And avoid blocking client connections

Back 67

use threads

Front 68

Back 68

Front 69

Back 69

Front 70

if we wanted to downcast a3 from Animal to Bird,

what must be done to make sure this will not yield errors?

Back 70

Front 71

In dynamic binding, the method called depends on the...

dynamic binding occurs during...

Back 71

class of the object referenced

runtime

(overriding methods, dynamic binding)

Front 72

Animal myanimal = new SongBird();

is

myanimal.sing();

legal?

Back 72

NO! animal does not know how to sing

Front 73

Animal myanimal = new SongBird();

is

myanimal.move();

legal?

Back 73

Yes, but interestingly SongBird does not have a move method so we go up the inheritance hierarchy and find that Bird overrides the move()

so "flying" would be printed, or something

Front 74

In static binding, the method called depends on the ...

static binding occurs during

Back 74

class of the variable

compilation time

Front 75

output?

Back 75

inside Collection sort method

because variable type was of Collection

Front 76

String s = "Guybrush";

s.substring(2,4) = ??

Back 76

"yb" stop at 4-1

Front 77

what happens if your exceptions are listed generic to specific?

Back 77

compilation error, unreachable code

Front 78

Back 78

know

Front 79

Back 79

in javax.swing

modal - wait until closed to continue program

JFileChooser

Front 80

Dynamic Data Structures offer....

Back 80

fluidity

Front 81

Abstract Data Type

Back 81

- exhibit a behavior, dont know how implemented

-stack

-queue

ex:

stack implemented via linkedList or array

Front 82

stack

Back 82

-pop

-push

-isEmpty

Last In First Out

Front 83

queue

Back 83

- add

- remove

- peek

ex print que

First In First Out

Front 84

break the problem down into two pieces

- basis case:

- recursice case:

Back 84

recursion

Front 85

recursion

Back 85

watch out for how many frames are made

proxy method to call recursive method

Front 86

traversing a binary search tree

Back 86