TreeSet | Notion

Modifier and Type	Method and Description
`boolean`	[`add](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#add-E->)([E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>) e)`Adds the specified element to this set if it is not already present.
`boolean`	[`addAll](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#addAll-java.util.Collection->)([Collection](<https://docs.oracle.com/javase/8/docs/api/java/util/Collection.html>)<? extends [E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>)> c)`Adds all of the elements in the specified collection to this set.
`E`	[`ceiling](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#ceiling-E->)([E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>) e)`Returns the least element in this set greater than or equal to the given element, or `null` if there is no such element.
`void`	[`clear](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#clear-->)()`Removes all of the elements from this set.
`Object`	[`clone](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#clone-->)()`Returns a shallow copy of this `TreeSet` instance.
[`Comparator](<https://docs.oracle.com/javase/8/docs/api/java/util/Comparator.html>)<? super [E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>)>`	[`comparator](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#comparator-->)()`Returns the comparator used to order the elements in this set, or null if this set uses the natural ordering of its elements.
`boolean`	[`contains](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#contains-java.lang.Object->)([Object](<https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html>) o)`Returns `true` if this set contains the specified element.
[`Iterator](<https://docs.oracle.com/javase/8/docs/api/java/util/Iterator.html>)<[E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>)>`	[`descendingIterator](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#descendingIterator-->)()`Returns an iterator over the elements in this set in descending order.
[`NavigableSet](<https://docs.oracle.com/javase/8/docs/api/java/util/NavigableSet.html>)<[E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>)>`	[`descendingSet](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#descendingSet-->)()`Returns a reverse order view of the elements contained in this set.
`E`	[`first](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#first-->)()`Returns the first (lowest) element currently in this set.
`E`	[`floor](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#floor-E->)([E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>) e)`Returns the greatest element in this set less than or equal to the given element, or `null` if there is no such element.
[`SortedSet](<https://docs.oracle.com/javase/8/docs/api/java/util/SortedSet.html>)<[E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>)>`	[`headSet](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#headSet-E->)([E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>) toElement)`Returns a view of the portion of this set whose elements are strictly less than toElement.
[`NavigableSet](<https://docs.oracle.com/javase/8/docs/api/java/util/NavigableSet.html>)<[E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>)>`	[`headSet](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#headSet-E-boolean->)([E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>) toElement, boolean inclusive)`Returns a view of the portion of this set whose elements are less than (or equal to, if `inclusive` is true) `toElement`.
`E`	[`higher](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#higher-E->)([E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>) e)`Returns the least element in this set strictly greater than the given element, or `null` if there is no such element.
`boolean`	[`isEmpty](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#isEmpty-->)()`Returns `true` if this set contains no elements.
[`Iterator](<https://docs.oracle.com/javase/8/docs/api/java/util/Iterator.html>)<[E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>)>`	[`iterator](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#iterator-->)()`Returns an iterator over the elements in this set in ascending order.
`E`	[`last](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#last-->)()`Returns the last (highest) element currently in this set.
`E`	[`lower](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#lower-E->)([E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>) e)`Returns the greatest element in this set strictly less than the given element, or `null` if there is no such element.
`E`	[`pollFirst](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#pollFirst-->)()`Retrieves and removes the first (lowest) element, or returns `null` if this set is empty.
`E`	[`pollLast](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#pollLast-->)()`Retrieves and removes the last (highest) element, or returns `null` if this set is empty.
`boolean`	[`remove](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#remove-java.lang.Object->)([Object](<https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html>) o)`Removes the specified element from this set if it is present.
`int`	[`size](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#size-->)()`Returns the number of elements in this set (its cardinality).
[`Spliterator](<https://docs.oracle.com/javase/8/docs/api/java/util/Spliterator.html>)<[E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>)>`	[`spliterator](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#spliterator-->)()`Creates a late-binding and fail-fast `Spliterator` over the elements in this set.
[`NavigableSet](<https://docs.oracle.com/javase/8/docs/api/java/util/NavigableSet.html>)<[E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>)>`	[`subSet](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#subSet-E-boolean-E-boolean->)([E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>) fromElement, boolean fromInclusive, [E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>) toElement, boolean toInclusive)`Returns a view of the portion of this set whose elements range from `fromElement` to `toElement`.
[`SortedSet](<https://docs.oracle.com/javase/8/docs/api/java/util/SortedSet.html>)<[E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>)>`	[`subSet](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#subSet-E-E->)([E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>) fromElement, [E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>) toElement)`Returns a view of the portion of this set whose elements range from fromElement, inclusive, to toElement, exclusive.
[`SortedSet](<https://docs.oracle.com/javase/8/docs/api/java/util/SortedSet.html>)<[E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>)>`	[`tailSet](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#tailSet-E->)([E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>) fromElement)`Returns a view of the portion of this set whose elements are greater than or equal to fromElement.
[`NavigableSet](<https://docs.oracle.com/javase/8/docs/api/java/util/NavigableSet.html>)<[E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>)>`	[`tailSet](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#tailSet-E-boolean->)([E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>) fromElement, boolean inclusive)`Returns a view of the portion of this set whose elements are greater than (or equal to, if `inclusive` is true) `fromElement`.

Modifier and Type	Method and Description
`boolean`	[`add](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#add-E->)([E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>) e)`Adds the specified element to this set if it is not already present.
`boolean`	[`addAll](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#addAll-java.util.Collection->)([Collection](<https://docs.oracle.com/javase/8/docs/api/java/util/Collection.html>)<? extends [E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>)> c)`Adds all of the elements in the specified collection to this set.
`E`	[`ceiling](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#ceiling-E->)([E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>) e)`Returns the least element in this set greater than or equal to the given element, or `null` if there is no such element.
`void`	[`clear](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#clear-->)()`Removes all of the elements from this set.
`Object`	[`clone](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#clone-->)()`Returns a shallow copy of this `TreeSet` instance.
[`Comparator](<https://docs.oracle.com/javase/8/docs/api/java/util/Comparator.html>)<? super [E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>)>`	[`comparator](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#comparator-->)()`Returns the comparator used to order the elements in this set, or null if this set uses the natural ordering of its elements.
`boolean`	[`contains](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#contains-java.lang.Object->)([Object](<https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html>) o)`Returns `true` if this set contains the specified element.
[`Iterator](<https://docs.oracle.com/javase/8/docs/api/java/util/Iterator.html>)<[E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>)>`	[`descendingIterator](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#descendingIterator-->)()`Returns an iterator over the elements in this set in descending order.
[`NavigableSet](<https://docs.oracle.com/javase/8/docs/api/java/util/NavigableSet.html>)<[E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>)>`	[`descendingSet](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#descendingSet-->)()`Returns a reverse order view of the elements contained in this set.
`E`	[`first](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#first-->)()`Returns the first (lowest) element currently in this set.
`E`	[`floor](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#floor-E->)([E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>) e)`Returns the greatest element in this set less than or equal to the given element, or `null` if there is no such element.
[`SortedSet](<https://docs.oracle.com/javase/8/docs/api/java/util/SortedSet.html>)<[E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>)>`	[`headSet](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#headSet-E->)([E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>) toElement)`Returns a view of the portion of this set whose elements are strictly less than toElement.
[`NavigableSet](<https://docs.oracle.com/javase/8/docs/api/java/util/NavigableSet.html>)<[E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>)>`	[`headSet](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#headSet-E-boolean->)([E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>) toElement, boolean inclusive)`Returns a view of the portion of this set whose elements are less than (or equal to, if `inclusive` is true) `toElement`.
`E`	[`higher](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#higher-E->)([E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>) e)`Returns the least element in this set strictly greater than the given element, or `null` if there is no such element.
`boolean`	[`isEmpty](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#isEmpty-->)()`Returns `true` if this set contains no elements.
[`Iterator](<https://docs.oracle.com/javase/8/docs/api/java/util/Iterator.html>)<[E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>)>`	[`iterator](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#iterator-->)()`Returns an iterator over the elements in this set in ascending order.
`E`	[`last](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#last-->)()`Returns the last (highest) element currently in this set.
`E`	[`lower](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#lower-E->)([E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>) e)`Returns the greatest element in this set strictly less than the given element, or `null` if there is no such element.
`E`	[`pollFirst](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#pollFirst-->)()`Retrieves and removes the first (lowest) element, or returns `null` if this set is empty.
`E`	[`pollLast](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#pollLast-->)()`Retrieves and removes the last (highest) element, or returns `null` if this set is empty.
`boolean`	[`remove](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#remove-java.lang.Object->)([Object](<https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html>) o)`Removes the specified element from this set if it is present.
`int`	[`size](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#size-->)()`Returns the number of elements in this set (its cardinality).
[`Spliterator](<https://docs.oracle.com/javase/8/docs/api/java/util/Spliterator.html>)<[E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>)>`	[`spliterator](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#spliterator-->)()`Creates a late-binding and fail-fast `Spliterator` over the elements in this set.
[`NavigableSet](<https://docs.oracle.com/javase/8/docs/api/java/util/NavigableSet.html>)<[E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>)>`	[`subSet](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#subSet-E-boolean-E-boolean->)([E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>) fromElement, boolean fromInclusive, [E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>) toElement, boolean toInclusive)`Returns a view of the portion of this set whose elements range from `fromElement` to `toElement`.
[`SortedSet](<https://docs.oracle.com/javase/8/docs/api/java/util/SortedSet.html>)<[E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>)>`	[`subSet](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#subSet-E-E->)([E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>) fromElement, [E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>) toElement)`Returns a view of the portion of this set whose elements range from fromElement, inclusive, to toElement, exclusive.
[`SortedSet](<https://docs.oracle.com/javase/8/docs/api/java/util/SortedSet.html>)<[E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>)>`	[`tailSet](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#tailSet-E->)([E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>) fromElement)`Returns a view of the portion of this set whose elements are greater than or equal to fromElement.
[`NavigableSet](<https://docs.oracle.com/javase/8/docs/api/java/util/NavigableSet.html>)<[E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>)>`	[`tailSet](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html#tailSet-E-boolean->)([E](<https://docs.oracle.com/javase/8/docs/api/java/util/TreeSet.html>) fromElement, boolean inclusive)`Returns a view of the portion of this set whose elements are greater than (or equal to, if `inclusive` is true) `fromElement`.