Collections and Generics

Question 1

Enumerate all the Collections

Answer 1

1. List
2. Set
3. Queue
4. Map

Question 2

Common collection method looks at how many elements are in the Collection

Answer 2

Collection.isEmpty(), Collection.size()

Question 3

Common collection method, provides an easy way to discard all elements of the Collection.

Answer 3

Collection.clear()

Question 4

Common collection method, checks if certain value is in the Collection.

Answer 4

Collection.contains()

Question 5

List implementations

Answer 5

1. Arraylist
2. LInkedLIsts
3. Vector
4. ArrayDeque

Question 6

List method, add elements to end

Answer 6

void add(E element)

Question 7

List method, Adds element at index and moves the rest toward the end

Answer 7

void add(int index, E element)

Question 8

List method, Returns element at index

Answer 8

E get(int index)

Question 9

List method, Returns first matching index or -1 if not found

Answer 9

int indexOf(Object o)

Question 10

List method, Returns last matching index or -1 if not found

Answer 10

int lastIndexOf(Object o)

Question 11

List method, Removes element at index and moves the rest toward the front

Answer 11

void remove(int index)

Question 12

List method, E set(int index, E e) Replaces element at index and returns original

Answer 12

E set(int index, E e)

Question 13

Set Interface Implementations

Answer 13

HashSet

TreeSet

Question 14

Navigable Set Interface, Returns greatest element that is < e, or null if no such element

Answer 14

E lower(E e)

Question 15

Navigable Set Interface, Returns greatest element that is <= e, or null if no such element

Answer 15

E floor(E e)

Question 16

Navigable Set Interface, Returns smallest element that is >= e, or null if no such element

Answer 16

E ceiling(E e)

Question 17

Navigable Set Interface, Returns smallest element that is > e, or null if no such element

Answer 17

E higher(E e)

Question 18

Queue Implementations

Answer 18

ArrayDeque

Question 19

Queue Method, Adds an element to the back of the queue and returns true or throws an exception

Answer 19

boolean add(E e)

Question 20

Queue Method, Returns next element or throws an exception if empty queue

Answer 20

E element()

Question 21

Queue Method, Adds an element to the back of the queue and returns whether successful

Answer 21

boolean offer(E e)

Question 22

Queue Method,Removes and returns next element or throws an exception if empty queue

Answer 22

E remove()

Question 23

Queue Method,Adds an element to the front of the queue

Answer 23

void push(E e)

Question 24

Queue Method,Removes and returns next element or returns null if empty queue

Answer 24

E poll()

Question 25

Queue Method,Returns next element or returns null if empty queue

Answer 25

E peek()

Question 26

Queue Method, Removes and returns next element or throws an exception if empty queue

Answer 26

E pop()

Question 27

Map Implementations

Answer 27

Hashmap | Tree Map

Question 28

Map Methods, Removes all keys and values from the map.

Answer 28

void clear()

Question 29

Map Methods, Returns whether the map is empty.

Answer 29

boolean isEmpty() Returns whether the map is empty.

Question 30

Map Methods, Returns the number of entries (key/value pairs) in the map.

Answer 30

int size()

Question 31

Map Methods, Returns the value mapped by key or null if none is mapped.

Answer 31

V get(Object key)

Question 32

Map Methods, Adds or replaces key/value pair. Returns previous value or null.

Answer 32

V put(K key, V value)

Question 33

Map Methods, Removes and returns value mapped to key. Returns null if none.

Answer 33

V remove(Object key)

Question 34

Map Methods, Returns whether key is in map.

Answer 34

boolean containsKey(Object key)

Question 35

Map Methods, Returns value is in map.

Answer 35

boolean containsValue(Object)

Question 36

Map Methods, Returns set of all keys.

Answer 36

Set keySet()

Question 37

Map Methods, Returns Collection of all values.

Answer 37

Collection values()

Question 38

Java 8 new Map interface methods

Answer 38

merge(), computeIfPresent, computeIfAbsent

Question 39

Map method, combine two maps

Answer 39

map.merge(BiFunction)

Question 40

Map method, executes a BiFunction if the key is present

Answer 40

Map.computeIfPresent(BiFunction)

Question 41

Map method, executes a Function if the key is not present

Answer 41

Map.computeIfAbsent(Function)