一：SortedSet接口
有序的Set，排序的标准为：设置的Comparator或者自然排序(compareTo()方法); 所有的元素必须实现Comparable接口或者Set设置了Comparator接口；| Method Summary | |
|---|---|
Comparator<? super E> |
comparator() Returns the comparator used to order the elements in this set, or null if this set uses the natural orderingof its elements. |
E |
first() Returns the first (lowest) element currently in this set. |
SortedSet<E> |
headSet(E toElement) Returns a view of the portion of this set whose elements are strictly less than toElement. |
E |
last() Returns the last (highest) element currently in this set. |
SortedSet<E> |
subSet(E fromElement, E toElement) Returns a view of the portion of this set whose elements range from fromElement, inclusive, to toElement, exclusive. |
SortedSet<E> |
tailSet(E fromElement) Returns a view of the portion of this set whose elements are greater than or equal to fromElement. |
二：NavigableSet接口
继承了SortedSet接口 增加了若干接口来获得离某个元素最近的一些元素；| Method Summary | |
|---|---|
E |
ceiling(E e) Returns the least element in this set greater than or equal to the given element, or null if there is no such element. |
Iterator<E> |
descendingIterator() Returns an iterator over the elements in this set, in descending order. |
NavigableSet<E> |
descendingSet() Returns a reverse order view of the elements contained in this set. |
E |
floor(E 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<E> |
headSet(E toElement) Returns a view of the portion of this set whose elements are strictly less than toElement. |
NavigableSet<E> |
headSet(E toElement, Returns a view of the portion of this set whose elements are less than (or equal to, if inclusive is true)toElement. |
E |
higher(E e) Returns the least element in this set strictly greater than the given element, or null if there is no such element. |
Iterator<E> |
iterator() Returns an iterator over the elements in this set, in ascending order. |
E |
lower(E e) Returns the greatest element in this set strictly less than the given element, or null if there is no such element. |
E |
pollFirst() Retrieves and removes the first (lowest) element, or returns null if this set is empty. |
E |
pollLast() Retrieves and removes the last (highest) element, or returns null if this set is empty. |
NavigableSet<E> |
subSet(E fromElement, Returns a view of the portion of this set whose elements range from fromElement to toElement. |
SortedSet<E> |
subSet(E fromElement, E toElement) Returns a view of the portion of this set whose elements range from fromElement, inclusive, to toElement, exclusive. |
SortedSet<E> |
tailSet(E fromElement) Returns a view of the portion of this set whose elements are greater than or equal to fromElement. |
NavigableSet<E> |
tailSet(E fromElement, Returns a view of the portion of this set whose elements are greater than (or equal to, if inclusive is true) fromElement. |
三：TreeMap
内部是通过NavigableMap的形式来存储的；public class TreeSet<E> extends AbstractSet<E> implements NavigableSet<E>, Cloneable, java.io.Serializable {
private transient NavigableMap<E, Object> m;