Chapter 7

Front 1

True or False? equals(), hashCode(), and toString() are private?

Back 1

False. They're public

Front 2

Why should you override toString()?

Back 2

So that System.out.println() or other methods can see something useful, like your object's state

Front 3

== compared to equals()

Back 3

== used to determine if two REFERENCE VARIABLES are meaningful equivalent

equals() determines if two OBJECTS are meaningfully equivalent

Front 4

If you don't override equals() what will happen to your objects. (In regards to hashing keys)

Back 4

Your objects won't be useful hashing keys

Front 5

If you don't override equals() what will happen to your objects. (In regards to different objects)

Back 5

Different objects can't be considered equal

Front 6

Stings and wrappers do what that make them good hashing keys?

Back 6

override equals()

Front 7

What should you do when you override equals()? (in regards to comparing objects)

Back 7

Use instanceof operator to be sure yo're evaluating an appropriate class and compare the objects' significant attributes

Front 8

If x.equals(y) is true, then what is true about x and y's hashcodes?

Back 8

They're equal

Front 9

What must you do to hashCode() if you override equals()?

Back 9

If you override equals() you must override hashCode()

Front 10

How are the keys and buckets distributed in an efficient hashCode()?

Back 10

The keys are evenly distributed across its buckets

Front 11

An overridden equals() must be ____________ as precise as its hashCode() mate

Back 11

at least

Front 12

What variables aren't appropriate for equals() and hashCode()?

Back 12

transient

Front 13

collection meaning:

Back 13

Represents the data structure in which objects are stored

Front 14

Collection meaning:

Back 14

java.util interface from which Set and List extend

Front 15

Collections meaning:

Back 15

A class that holds static collection utility methods

Front 16

Definition of "Lists of things":

Back 16

Ordered, duplicates allowed, with an index

Front 17

Definition of "Sets of things":

Back 17

May or may not be ordered and/or sorted; duplicates NOT allowed

Front 18

Definition of "Maps of things with keys":

Back 18

May or may not be ordered and/or sorted; duplicate keys are NOT allowed

Front 19

Definition of "Queues of things to process":

Back 19

Ordered by FIFO or by property

Front 20

Definition of Ordered:

Back 20

Iterating through a collection in a specific, non-random order

Front 21

Definition of Sorted:

Back 21

Iterating through a collection in a sorted order

Front 22

Key Attributes of Common Collection Classes ArrayList:

Back 22

Fast iteration and fast random access

Front 23

Key Attributes of Common Collection Classes Vector:

Back 23

Like a slower ArrayList, but it has synchronized methods

Front 24

Key Attributes of Common Collection Classes LinkedList:

Back 24

Good for adding elements to the ends, i.e., stacks and ques

Front 25

Key Attributes of Common Collection Classes HashSet:

Back 25

Fast access, assures no duplicates, provides no ordering

Front 26

Key Attributes of Common Collection Classes LinkedHashSet:

Back 26

No duplicates; iterates by INSERTION order

Front 27

Key Attributes of Common Collection Classes TreeSet:

Back 27

No duplicates;iterates in SORTED order

Front 28

Key Attributes of Common Collection Classes HashMap:

Back 28

Fastest updates (key/values); allows one null key, many null values

Front 29

Key Attributes of Common Collection Classes Hashtable:

Back 29

Like a slower HashMap (as with Vector, due to its synchronized methods). No null values or null keys allowed

Front 30

Key Attributes of Common Collection Classes LinkedHashMap:

Back 30

Faster iterations; iterates by INSERTION ORDER OR LAST ACCESSED; allows one null key, many null values

Front 31

Key Attributes of Common Collection Classes TreeMap:

Back 31

A sorted map

Front 32

Key Attributes of Common Collection Classes PriorityQueue:

Back 32

A to-do list ordered by the elements' priority

Front 33

Collections hold only ________?

But what about primitives?

Back 33

Collections hold only Objects, but primitives can be autoboxed

Front 34

Iterator hasNext():

Back 34

determines if more elements exist; the Iterator does NOT move

Front 35

Iterator next()

Back 35

returns the next element AND moves the Iterator forward

Front 36

What must a Map's keys do to correctly use Collection classes?

Back 36

A map's keys must override equals() and hashCode()

Front 37

Queues use offer() to...

Back 37

add an element

Front 38

Queues use poll() to...

Back 38

remove the head f the queue

Front 39

Queues use peek() to...

Back 39

look at the head of the queue

Front 40

HashMap (Map/Set/List, ordered, sorted)

Back 40

Map

NOT ordered

NOT sorted

Front 41

Hashtable (Map/Set/List, ordered, sorted)

Back 41

Map

NOT ordered

NOT sorted

Front 42

TreeMap (Map/Set/List, ordered, sorted)

Back 42

Map

Ordered

Sorted (by natural or custom comparison rules)

Front 43

LinkedHashMap (Map/Set/List, ordered, sorted)

Back 43

Map

Ordered by insertion order or last access order

NOT sorted

Front 44

HashSet (Map/Set/List, ordered, sorted)

Back 44

Set

NOT ordered

NOT sorted

Front 45

TreeSet(Map/Set/List, ordered, sorted)

Back 45

Set

Ordered

Sorted by natural order or custom comparison rules

Front 46

LinkedHashSet(Map/Set/List, ordered, sorted)

Back 46

Set

Ordered by insertion order

NOT sorted

Front 47

ArrayList (Map/Set/List, ordered, sorted)

Back 47

List

Ordered by index

NOT sorted

Front 48

Vector (Map/Set/List, ordered, sorted)

Back 48

List

Ordered by index

NOT sorted

Front 49

LinkedList (Map/Set/List, ordered, sorted)

Back 49

List

Ordered by index

NOT sorted

Front 50

PriorityQueue (Map/Set/List, ordered, sorted)

Back 50

NONE

Sorted

Sorted by to-do order

Front 51

You can create/extend "backed" sub-copies of which two Common Collection Classes?

Back 51

TreeSets

TreeMaps

Front 52

What must we do first to start sorting and searching Arrays and Lists so that it provides ONLY ONE sort order?

Back 52

Implement Comparable using compareTo()

Front 53

How do we create MANY Comparators to sort a class in many ways?

Back 53

Implement compare()

Front 54

What must happen to an Array or List before it can be searched?

Back 54

The Array or List must be sorted first

Front 55

Difference between lower() and floor()

Back 55

lower() returns the element less than the given element, and floor() returns the element less than OR EQUAL TO the given element

Front 56

Difference between higher() and ceiling()

Back 56

higher() returns the element greater than the given element

ceiling() returns the element greater OR EQUAL TO the given element

Front 57

java.util Utility Classes (two of them):

Back 57

Collections

Arrays

Front 58

binarySearch() method

Back 58

Search a pre-sorted Array or List

Front 59

Array.asList()

Back 59

Creates a List from an array and links them together

Front 60

Collections.reverse

Back 60

Reverses the order of elements in a List

Front 61

Collections.reverseOrder()

Back 61

Returns a Comparator that sorts in reverse

Front 62

What do Generics allow you to do?

Back 62

They let you enforce compile-time type safety on Collections (or other classes and methods declared using generic type parameters)

Front 63

What kind of references can an ArrayList <Animal> accept?

Back 63

Animal or any subclass of it

Front 64

When is a cast NOT needed to get (declared type) elements out of the collection?

Back 64

When using generic collections

Non-generic collections REQUIRE a cast

Front 65

True or False? You can pass a generic collection into a method that takes a NON-generic collection?

Back 65

True, but the results may be disastrous

Front 66

True or False? A compilation WARNING is considered a compilation ERROR or FAILURE

Back 66

False

Front 67

When does Generic type information exist?

Back 67

NOT at runtime

It is a compile-time safety only

Front 68

Polymorphic assignments applies only to the ______ type, not the ________ type parameter

Back 68

base

generic

Front 69

Which one can you say?

List<Animal> aList = new ArrayList<Animal>();

List<Animal> aList= new ArrayList<Dog>();

Back 69

List<Animal> aList = new ArrayList <Animal>();

Because Polymorphic assignments apply only to BASE types, NOT the generic type parameter

Front 70

Where does the polymorphic assignment rule apply to?

Back 70

Everywhere an assignment can be made.

Front 71

Why don't these two lines of code work? (different reasons)

void foo(List<Animal> aList) {}

List<Animal> bar() {}

Back 71

First one cannot TAKE a List<Dog>

Second one cannot RETURN a List<Dog>

Front 72

Wildcard syntax allows for a generic method to...

Back 72

accept subtypes (or supertypes) or the declared type of the method argument

Front 73

Wildcard syntax. What can this method take?

void addD(List<Dog> d) {}

Back 73

Can take only <Dog>

Front 74

Wildcard syntax. What can this method take?

void addD(List<? extends Dog>){}

Back 74

Can take <Dog> or a subclass of dog

Front 75

The wildcard keyword extends is used to mean either _________ or __________

Back 75

extends

implements

Front 76

When using a wildcard, <? extends Dog>, what can the collection do and not do?

Back 76

The collection can be accessed but NOT modified

Front 77

When using a wildcard, List<?>, what type can be assigned to the reference?

Is it for modifications?

Back 77

Any generic type can be assigned to the reference, but for access ONLY, NO modifications

Front 78

What type of object can List<?> or List<? extends Object> hold?

Anything special about the object?

Back 78

It can hold any type of OBJECT.

For access ONLY.

Front 79

What do T and E mean for declaration conventions for generics?

Back 79

T: for type

E: for element

Front 80

The generics type identifier can be used in...

Back 80

class, method, and variable declaration

class Foo<t> {}

T anInstance;

Foo(T aRef) {}

Front 81

True or False? You can use more than one parameterized type in a declaration?

public class UseTwo<T, X> {}

Back 81

True

Front 82

True or False? You can declare a generic method using a type NOT defined in the class?

public <T> void makeList (T t) {}

Back 82

True

This method has a void return type, but to use T within the method's argument you must declare the <T>, which happens before the return type