Chapter 3 - Assignments

Question 1

Local Variables

Answer 1

Live on the stack

Question 2

Objects and instance Variables

Answer 2

Live on the Heap

Question 3

Integer literals

Answer 3

can be decimal, octal, or hexadecimal

Question 4

Float literals end in

Answer 4

F or f

Question 5

Double literals end in

Answer 5

D or d

Question 6

Boolean literals

Answer 6

are true and false

Question 7

scope

Answer 7

refers to the lifetime of a variable

Question 8

4 basic scopes

Answer 8

1. Static variables live basically as long as their class lives
2. Instance variables live as long as their object lives
3. Local variables live as long as their method
4. Block variables live until the block completes

Question 9

Literal integers

Answer 9

are implicitly ints

Question 10

integer expressions

Answer 10

always end in a int-sized result, never smaller

Question 11

floating point numbers

Answer 11

are implicitly doubles (64 bits)

Question 12

Narrowing primatives

Answer 12

truncates the high order bits

Question 13

Compound assignments (eg +=)

Answer 13

perform an automatic cast

Question 14

A reference variable

Answer 14

holds bits that are used to refer to an object

Question 15

Reference variables

Answer 15

can refer to subclasses of the declared type but not to the superclasses

Question 16

When creating an object (new keyword), 3 things happen

Answer 16

1. ) Make a reference variable
2. ) Create a new Object
3. ) Assign object to the reference variable

Question 17

Array objects that are uninitialized

Answer 17

when instantiated, objects within the array are not initialized automatically, but all reference get the default value of null.

Question 18

Array primatives

Answer 18

when instantiated receive their default values

Question 19

Instance variables

Answer 19

always initialized with their default value

Question 20

local/automatic/method variables

Answer 20

never given a default value, if you attempt to use one before initializing you will get a compiler error

Question 21

Methods

Answer 21

can take primitive and/or object references as arguments

Question 22

Method arguments

Answer 22

are always copies

Question 23

Method arguments

Answer 23

are never actual objects (they can be references to objects)

Question 24

A primitive argument

Answer 24

is unattached copy of the original primative

Question 25

A reference argument

Answer 25

is another copy of a reference to the original object

Question 26

Shadowing

Answer 26

occurs when two variables with different scopes share the same name

Question 27

Arrays

Answer 27

can hold primitives or objects, but the array itself is always an Object

Question 28

When you declare an array

Answer 28

the brackets can be left or right of the name

Question 29

Array size

Answer 29

it is never legal to declare the size of an array in the declaration

Question 30

You must include the size of an array when you construct it

Answer 30

(using new) unless you are creating an anonymous array.

Question 31

Elements in an array of objects

Answer 31

are not automatically created, although primitive array elements are given their default values

Question 32

You will get a NullPointerException

Answer 32

if you try to use an array element in an object array if that element does not refer to a real object

Question 33

arrays

Answer 33

are indexed beginning with 0

Question 34

An ArrayIndexOutOfBoundsException

Answer 34

occurs if you use a bad index value

Question 35

Arrays have a length variable

Answer 35

whose value is the number of array elements

Question 36

Last index in an array

Answer 36

is always one less than the length of the array

Question 37

Multidimensional Arrays

Answer 37

are just arrays of arrays

Question 38

The dimensions in a multidimensional array

Answer 38

can have different lengths

Question 39

Array primitives

Answer 39

can accept any value that can be promoted implicitly to the array's declared data type.

Question 40

An array of objects

Answer 40

can hold any object that passes an IS-A test for the declared type of array.

Question 41

If you assign an array to a previously assigned array reference

Answer 41

the array you are assigning must have the same dimension as the reference your assigning it to

Question 42

You can assign an array of one type

Answer 42

to a previously declared array of one of its supertypes.

Question 43

Static initialization blocks

Answer 43

run once when the class is first loaded

Question 44

Instance initialization blocks

Answer 44

run every time a new instance is created. They run after ALL super-constructors, and before the constructor's code has run

Question 45

If multiple init blocks exist in a class

Answer 45

they follow the previous 2 rules on initialization AND they run in the order in which they appear in the source file.

Question 46

The wrapper class

Answer 46

correlate to the primitive types

Question 47

Wrappers have 2 main fuctions

Answer 47

1. to wrap primitives so they can be handled like objects. | 2. to provide utility methods for primitives (usually conversions)

Question 48

The 3 most important method families are

Answer 48

1. xxxValue(); takes no args, returns primitive 2. parseXXX();takes a string, returns primative, throws NFE 3. valueOf; takes a String, returns a wrapped object, throws NFE

Question 49

Wrapper constructors

Answer 49

can take a string or a Primitive, except for Character, which can take a char.

Question 50

Radix refers to

Answer 50

bases other than 10; octal is radix = 8, hex = 16

Question 51

Boxing

Answer 51

as of Java 5, allows you to convert primitives to wrappers or to convert wrappers to primitives automatically.

Question 52

Using == with wrappers created through boxing

Answer 52

those with the same small values, typically lower than 127 will be ==; larger values will NOT be ==

Question 53

Primitive widening

Answer 53

uses the "smallest" method argument possible

Question 54

used individually, boxing and var-args

Answer 54

are compatible with overloading

Question 55

You CANNOT widen from one wrapper type to another

Answer 55

IS-A fails

Question 56

You CANNOT widen and then box

Answer 56

An int can't become a long

Question 57

You can box then widen

Answer 57

An int can become an Object, via an Integer

Question 58

You can combine var-args with either

Answer 58

widening or boxing

Question 59

Garbage collection

Answer 59

Java provides automatic memory management

Question 60

Purpose of GC

Answer 60

delete objects which can't be reached

Question 61

Only the JVM

Answer 61

decides when to run GC, you can only suggest it

Question 62

Object must be considered "eligible"

Answer 62

before they can be garbage collected

Question 63

An object is eligible for GC

Answer 63

when no live thread can reach it.

Question 64

To reach a thread

Answer 64

you must have a live, reachable reference to that object.

Question 65

Islands of objects

Answer 65

can be GCed, even though they refer to each other

Question 66

Class Object

Answer 66

has a finalize() method

Question 67

The finalize() method

Answer 67

is guaranteed to run once and only once before the GC deletes an object

Question 68

GC makes no guarantees

Answer 68

finalize() may never run

Question 69

You can uneligibilize an object for th GC

Answer 69

within finalize()

Question 70

Primitive Data Types

Answer 70

Be careful bears shouldn't ingest large furry dogs. Boolean, char, byte, short, int, long, float double 8,16,32,64,32,64

Question 71

Roses are red,, violets are blue

Answer 71

extend only one, but implement two

Question 72

Instance variables are assigned a default value

Answer 72

even if you don't explicitly assign one. The default values are 0/0.0/false for primitives, and null for references.

Question 73

Roses are red, violets are blue

Answer 73

Your parents come first, way before you... The superclass parts of an object must be fully formed before the new subclass object can exist.

Question 74

A final

Answer 74

``` variable means you can't change it's value, method means you can't override the method, class means you can't extend the class ```