Collections Methods

Question 1

Collection boolean add(Element elem)

Answer 1

Adds elem into the underlying container

Question 2

Collection void clear()

Answer 2

Removes all elements from the container

Question 3

Collection boolean isEmpty()

Answer 3

Returns true if empty, false if not.

Question 4

Collection Iterator iterator()

Answer 4

Returns an Iterator object for iterating over the container.

Question 5

Collection int size()

Answer 5

Returns the number of elements in the container

Question 6

Collection Object[] toArray()

Answer 6

Returns an array that has all elements in the container.

Question 7

Collection boolean addAll(Collection extends element> coll)

Answer 7

Adds all the elements in coll into the underlying container

Question 8

Collection boolean containsAll(Collection> coll)

Answer 8

Checks if all elements given in coll are present in the underlying container.

Question 9

Collection boolean removeAll(Collection> coll)

Answer 9

Removes all elements from the underlying container that are also present in coll.

Question 10

Collection boolean retainAll(Collection> coll)

Answer 10

Retains elements in the underlying container only if they are also present in coll; removes all other elements.

Question 11

Iterator boolean hasNext()

Answer 11

Returns true if there are more elements to traverse.

Question 12

Iterator E next()

Answer 12

Moves the iterator to the next element and returns that element.

Question 13

Iterator void remove()

Answer 13

Removes the last visited element from the underlying container. next() must be called before calling remove, otherwise throws IllegalStateException.

Question 14

ListIterator boolean hasPrevious()

Answer 14

Checks if the iterator has more elements to traverse in the previous direction.

Question 15

ListIterator Element previous()

Answer 15

Moves the iterator to the next element and returns that next element in reverse direction()

Question 16

ListIterator int nextIndex()

Answer 16

Returns the index of the next element in forward direction.

Question 17

ListIterator int previousIndex()

Answer 17

Returns the index of the next element in reverse direction.

Question 18

ListIterator void set(Element element)

Answer 18

Replaces the last element visited (using next or previous) with element.

Question 19

ListIterator void add(Element element)

Answer 19

Adds the element to the list at the current iteration position.

Question 20

Deque void addFirst(Element element)

Answer 20

Adds the element to the front of the deque. Raises Exception if full.

Question 21

Deque void addLast(Element element)

Answer 21

Adds the element to the end of the deque. Raises Exception if full.

Question 22

Deque Element removeFirst()

Answer 22

Removes an element from the front of the Deque and returns it. Raises NoSuchElementException if empty.

Question 23

Deque Element removeLast()

Answer 23

Removes and returns the element at the end of the deque. Raises NoSuchElementException if empty.

Question 24

Deque Element getFirst()

Answer 24

Returns the first element from the Deque, does not remove. Raises NoSuchElementException if empty.

Question 25

Deque Element getLast()

Answer 25

Returns the last element from the Deque, does not remove. Raises NoSuchElementException if empty.

Question 26

Deque boolean offerFirst(element)

Answer 26

Returns true if the element was added to the front, false if the deque is full.

Question 27

Deque boolean offerLast(element)

Answer 27

Returns true if the element was added to the back, false if the deque is full.

Question 28

Deque Element pollFirst()

Answer 28

Removes and returns an element from the front. Returns null if the deque is empty.

Question 29

Deque Element pollLast()

Answer 29

Removes and returns an element from the back. Returns null if the deque is empty.

Question 30

Deque Element peekFirst()

Answer 30

Returns but does not remove the first element. Returns null if the deque is empty.

Question 31

Deque Element peekLast()

Answer 31

Returns but does not remove the last element. Returns null if the deque is empty.