TreeSet -
1) pollFirst() - removes the first entry
2) pollLast() - removes the last entry.
3) descendingSet() - in reverse order
TreeMap -
1) pollFirstEntry() - removes the first entry
2) pollLastEntry() - removes the last entry.
3) descendingMap() - in reverseOrder.
9) PriorityQueue -
- offers three new methods - peek, poll, offer
- offer is to add elements.
- poll() removes the highest priority value from the queue.
- peek() displays the highest priority value without removing from the queue.
10) Generics -
- To ensure safe collection. From java 5 they have introduced Generics.
- Running mix of generic and non-generic code may result in run-time errors.
- Non - generic get methods should return Objects .
- Type safety is only done at compiler and not at runtime.
- UnBoxing occurs only when the object is Long or Integer. Unboxing cannot convert general Object to an primitive int.
11) Polymorphism and Generics.
- Polymorphism dont apply for generics.
- Generic Methods wont accept polymorphic arguments.
- we can add instances of subtypes into the collection even though the collection is supertype specific. (same as array).
- In generic methods we cannot use add() method. the method declaration will look something like this
(List<? extends Animal> animal) - but cannnot add any thing
- (List <? super Dog> animal) - accept all the parameters that are dog and super to dog.
(List <?> animal) - takes any generic list but you are not supposed to add any thing.
12) Creating Generic classes.
- class name <T>
write the code.
13) Generic methods
* public <T> void methodName() - declare type variable first.
-
*A null cannot be autoboxed to 0.
* for subtree headset (x,true) means include x
* for subtree .tailset(x,true) means exclude x
1) pollFirst() - removes the first entry
2) pollLast() - removes the last entry.
3) descendingSet() - in reverse order
TreeMap -
1) pollFirstEntry() - removes the first entry
2) pollLastEntry() - removes the last entry.
3) descendingMap() - in reverseOrder.
9) PriorityQueue -
- offers three new methods - peek, poll, offer
- offer is to add elements.
- poll() removes the highest priority value from the queue.
- peek() displays the highest priority value without removing from the queue.
10) Generics -
- To ensure safe collection. From java 5 they have introduced Generics.
- Running mix of generic and non-generic code may result in run-time errors.
- Non - generic get methods should return Objects .
- Type safety is only done at compiler and not at runtime.
- UnBoxing occurs only when the object is Long or Integer. Unboxing cannot convert general Object to an primitive int.
11) Polymorphism and Generics.
- Polymorphism dont apply for generics.
- Generic Methods wont accept polymorphic arguments.
- we can add instances of subtypes into the collection even though the collection is supertype specific. (same as array).
- In generic methods we cannot use add() method. the method declaration will look something like this
(List<? extends Animal> animal) - but cannnot add any thing
- (List <? super Dog> animal) - accept all the parameters that are dog and super to dog.
(List <?> animal) - takes any generic list but you are not supposed to add any thing.
12) Creating Generic classes.
- class name <T>
write the code.
13) Generic methods
* public <T> void methodName() - declare type variable first.
-
*A null cannot be autoboxed to 0.
* for subtree headset (x,true) means include x
* for subtree .tailset(x,true) means exclude x
