Collections and Generics Flashcards
Enumerate all the Collections
- List
- Set
- Queue
- Map
Common collection method looks at how many elements are in the Collection
Collection.isEmpty(), Collection.size()
Common collection method, provides an easy way to discard all elements of the Collection.
Collection.clear()
Common collection method, checks if certain value is in the Collection.
Collection.contains()
List implementations
- Arraylist
- LInkedLIsts
- Vector
- ArrayDeque
List method, add elements to end
void add(E element)
List method, Adds element at index and moves the rest toward the end
void add(int index, E element)
List method, Returns element at index
E get(int index)
List method, Returns first matching index or -1 if not found
int indexOf(Object o)
List method, Returns last matching index or -1 if not found
int lastIndexOf(Object o)
List method, Removes element at index and moves the rest toward the front
void remove(int index)
List method, E set(int index, E e) Replaces element at index and returns original
E set(int index, E e)
Set Interface Implementations
HashSet
TreeSet
Navigable Set Interface, Returns greatest element that is < e, or null if no such element
E lower(E e)
Navigable Set Interface, Returns greatest element that is <= e, or null if no such element
E floor(E e)
Navigable Set Interface, Returns smallest element that is >= e, or null if no such element
E ceiling(E e)
Navigable Set Interface, Returns smallest element that is > e, or null if no such element
E higher(E e)
Queue Implementations
ArrayDeque
Queue Method, Adds an element to the back of the queue and returns true or throws an exception
boolean add(E e)
Queue Method, Returns next element or throws an exception if empty queue
E element()
Queue Method, Adds an element to the back of the queue and returns whether successful
boolean offer(E e)
Queue Method,Removes and returns next element or throws an exception if empty queue
E remove()
Queue Method,Adds an element to the front of the queue
void push(E e)
Queue Method,Removes and returns next element or returns null if empty queue
E poll()
Queue Method,Returns next element or returns null if empty queue
E peek()
Queue Method, Removes and returns next element or throws an exception if empty queue
E pop()
Map Implementations
Hashmap
Tree Map
Map Methods, Removes all keys and values from the map.
void clear()
Map Methods, Returns whether the map is empty.
boolean isEmpty() Returns whether the map is empty.
Map Methods, Returns the number of entries (key/value pairs) in the map.
int size()
Map Methods, Returns the value mapped by key or null if none is mapped.
V get(Object key)
Map Methods, Adds or replaces key/value pair. Returns previous value or null.
V put(K key, V value)
Map Methods, Removes and returns value mapped to key. Returns null if none.
V remove(Object key)
Map Methods, Returns whether key is in map.
boolean containsKey(Object key)
Map Methods, Returns value is in map.
boolean containsValue(Object)
Map Methods, Returns set of all keys.
Set keySet()
Map Methods, Returns Collection of all values.
Collection values()
Java 8 new Map interface methods
merge(), computeIfPresent, computeIfAbsent
Map method, combine two maps
map.merge(BiFunction)
Map method, executes a BiFunction if the key is present
Map.computeIfPresent(BiFunction)
Map method, executes a Function if the key is not present
Map.computeIfAbsent(Function)
