Java Data Structures

init a HashMap mapping strings to integers with the variable name 'map'

Map<String, Integer> map = new HashMap<>();

method to add an entry to a HashMap

put(key, item)

method to retrieve an item from a HashMap

get(key)

method to retrieve an item from a HashMap with a default value

getOrDefault(key, default)

method to check if a key exists in a HashMap

containsKey(key)

method to remove an item from a HashMap

remove(key)

method to check the number of entries in a HashMap

size()

init a list containing integers named 'list' that is empty

List<Integer> list = new ArrayList<>();

method to append an item to a list

add(item)

method to insert an item to a list at an index

add(index, item)

method to index a List

get(index)

Method to update an index of a List

set(index, item)

method to remove an index from a List

remove(index)

method to sort a List

Collections.sort(list)

method to reverse a List

Collections.reverse(list)

init a Hashset containing Integers named 'set'

Set set = new HashSet<>();

method to add an item to a HashSet

add(item)

method to check if an item exists in a HashSet

contains(item)

method to remove an item from a HashSet

remove(item)

method to do a union on a HashSet

addAll(other)

method to do a intersection on a HashSet

retainAll(other)

init a deque named 'dq' containing Integers

Deque dq = new ArrayDeque<>();

method to enqueue into a Deque

offerLast(item)

method to dequeue from a Deque

pollFirst()

method to peek the first item in a Deque

peekFirst()

method to push an item onto a Deque

push(item)

method to pop an item from a Deque

pop()

method to peek the top of a Deque

peek()

init a min heap named 'minHeap' that contains integers

PriorityQueue minHeap = new PriorityQueue<>();

method to add an item to a Heap

add(item)

method to pop the next item from a Heap

poll()

method to look at the next item in a Heap

peek()

init a maxHeap named 'maxHeap' containing integers

PriorityQueue maxHeap = new PriorityQueue<>(Collections.reverseOrder());