SortedSet接口源码解析

SortedSet接口为TreeSet做准备
可以实现排序集合
源码

package java.util;

public interface SortedSet<E> extends Set<E> {
    /**
     * 比较器
     */
    Comparator<? super E> comparator();

    /**
     * 获取子集
     * @throws ClassCastException if <tt>fromElement</tt> and
     *         <tt>toElement</tt> cannot be compared to one another using this
     *         set‘s comparator (or, if the set has no comparator, using
     *         natural ordering).  Implementations may, but are not required
     *         to, throw this exception if <tt>fromElement</tt> or
     *         <tt>toElement</tt> cannot be compared to elements currently in
     *         the set.
     * @throws NullPointerException if <tt>fromElement</tt> or
     *         <tt>toElement</tt> is null and this set does not permit null
     *         elements
     * @throws IllegalArgumentException if <tt>fromElement</tt> is
     *         greater than <tt>toElement</tt>; or if this set itself
     *         has a restricted range, and <tt>fromElement</tt> or
     *         <tt>toElement</tt> lies outside the bounds of the range
     */
    SortedSet<E> subSet(E fromElement, E toElement);

    /**
     * 获取严格小于toElement的子集
     *
     * @param toElement high endpoint (exclusive) of the returned set
     * @return a view of the portion of this set whose elements are strictly
     *         less than <tt>toElement</tt>
     * @throws ClassCastException if <tt>toElement</tt> is not compatible
     *         with this set‘s comparator (or, if the set has no comparator,
     *         if <tt>toElement</tt> does not implement {@link Comparable}).
     *         Implementations may, but are not required to, throw this
     *         exception if <tt>toElement</tt> cannot be compared to elements
     *         currently in the set.
     * @throws NullPointerException if <tt>toElement</tt> is null and
     *         this set does not permit null elements
     * @throws IllegalArgumentException if this set itself has a
     *         restricted range, and <tt>toElement</tt> lies outside the
     *         bounds of the range
     */
    SortedSet<E> headSet(E toElement);

    /**
     * 获取大于等于fromElement的子集 
     *
     * @param fromElement low endpoint (inclusive) of the returned set
     * @return a view of the portion of this set whose elements are greater
     *         than or equal to <tt>fromElement</tt>
     * @throws ClassCastException if <tt>fromElement</tt> is not compatible
     *         with this set‘s comparator (or, if the set has no comparator,
     *         if <tt>fromElement</tt> does not implement {@link Comparable}).
     *         Implementations may, but are not required to, throw this
     *         exception if <tt>fromElement</tt> cannot be compared to elements
     *         currently in the set.
     * @throws NullPointerException if <tt>fromElement</tt> is null
     *         and this set does not permit null elements
     * @throws IllegalArgumentException if this set itself has a
     *         restricted range, and <tt>fromElement</tt> lies outside the
     *         bounds of the range
     */
    SortedSet<E> tailSet(E fromElement);

    /**
     * 第一个元素 
     *
     * @return the first (lowest) element currently in this set
     * @throws NoSuchElementException if this set is empty
     */
    E first();

    /**
     * 最后一个元素
     *
     * @return the last (highest) element currently in this set
     * @throws NoSuchElementException if this set is empty
     */
    E last();
}