Sets and Maps

what is a set?

a collection of unique elements with no duplicates

how do you check is an element is in a set?

set.contains(element)

can sets store duplicate values?

no

do sets support indexing like lists?

no

key operations of a set?

add, remove, contains, size, isEmpty

when should you use a set?

when you need fast lookup and no duplicates

what is a limitation of sets compared to lists?

cannot access elements by position

what is a map?

a collection that stores key-value pairs

what is the purpose of a key in a map?

to uniquely identify and retrieves its associated value

can a map have duplicate keys?

no

what happens if you call get(key) and the key does not exist?

returns null

how do you insert into a map?

map.put(key, value)

how do you check if a key exists?

map.containsKey(key)

What is more efficient: containsKey + get OR just get?

just get (avoids double lookup)

how do you remove an entry from a map?

map.remove(key)

how do you iterate over keys?

for (K key: map.keySet())

how do you iterate over key-value pairs efficiently?

for (Map.Entry<K,V> e : map.entrySet())

what does entrySet() return?

a set of key-value pairs

what does values() return?

a collection of all values in the map

what is a multimap?

a map where one key can have multiple values

does Java support multimaps directly?

no

how do you implement a multimap in Java?

use Map<K, List<V>>

what is the key pattern for adding to a multimap?

1. get list

2. if null → create list

3. add value

what does modifying the list affect the map?

because the list reference is stored in the map

what does the mimic program do?

generates text based on patterns from a sample document

what data structure stores sentence starters?

ArrayList<String>

what data structure stores word relationships?

Map<String, ArrayList<String>>

what does the followers map represent?

a word mapped to all words that followed it in the text

how is the next word generated?

randomly chosen from the list of followers

what happens if a word has no followers?

pick a random sentence starter

why keep punctuation and capitalization?

to make generated text look more realistic

what algorithm concept is this mimic model similar to?

a simple Markov chain