java集合类分析-Treeset

//从下面的treeset的源代码可以看出它基本上就是treeMap的一层包装，因此这里过多的介绍，详细可以看treeMap的具体的实现//实现了NavigableSet、以及set接口 其中NavigableSet实现的是sortSet接口
public class TreeSet<E> extends AbstractSet<E>
    implements NavigableSet<E>, Cloneable, java.io.Serializable
{
  ///这里就可以看出treeset和hashset 一样是基于map实现的
    private transient NavigableMap<E,Object> m;
    // 构建一个至当作map中的值
    private static final Object PRESENT = new Object();
    TreeSet(NavigableMap<E,Object> m) {
        this.m = m;
    }
    //可以看出实际是treemap
    public TreeSet() {
        this(new TreeMap<E,Object>());
    }
  //策略模式制定定制的比较器但是内部感受不到
    public TreeSet(Comparator<? super E> comparator) {
        this(new TreeMap<>(comparator));
    }
    public TreeSet(Collection<? extends E> c) {
        this();
        addAll(c);
    }
    public TreeSet(SortedSet<E> s) {
        this(s.comparator());
        addAll(s);
    }

    //返回值迭代器 根据制定的比较器返回结果
    public Iterator<E> iterator() {
        return m.navigableKeySet().iterator();
    }

    public Iterator<E> descendingIterator() {
        return m.descendingKeySet().iterator();
    }
    public NavigableSet<E> descendingSet() {
        return new TreeSet<>(m.descendingMap());
    }

    public int size() {
        return m.size();
    }
    public boolean isEmpty() {
        return m.isEmpty();
}
//判断是不是含有该元素
    public boolean contains(Object o) {
        return m.containsKey(o);
    }
   //添加元素
    public boolean add(E e) {
        return m.put(e, PRESENT)==null;
    }
//删除元素
public boolean remove(Object o) {
        return m.remove(o)==PRESENT;
    }

   //清空map
    public void clear() {
        m.clear();
    }

    public  boolean addAll(Collection<? extends E> c) {
        // Use linear-time version if applicable
        if (m.size()==0 && c.size() > 0 &&
            c instanceof SortedSet &&
            m instanceof TreeMap) {
            SortedSet<? extends E> set = (SortedSet<? extends E>) c;
            TreeMap<E,Object> map = (TreeMap<E, Object>) m;
            Comparator<? super E> cc = (Comparator<? super E>) set.comparator();
            Comparator<? super E> mc = map.comparator();
            if (cc==mc || (cc != null && cc.equals(mc))) {
                map.addAllForTreeSet(set, PRESENT);
                return true;
            }
        }
        return super.addAll(c);
    }

    public NavigableSet<E> subSet(E fromElement, boolean fromInclusive,
                                  E toElement,   boolean toInclusive) {
        return new TreeSet<>(m.subMap(fromElement, fromInclusive,
                                       toElement,   toInclusive));
    }
    public NavigableSet<E> headSet(E toElement, boolean inclusive) {
        return new TreeSet<>(m.headMap(toElement, inclusive));
    }
    public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
        return new TreeSet<>(m.tailMap(fromElement, inclusive));
    }
    public SortedSet<E> subSet(E fromElement, E toElement) {
        return subSet(fromElement, true, toElement, false);
    }
    public SortedSet<E> headSet(E toElement) {
        return headSet(toElement, false);
    }
    public SortedSet<E> tailSet(E fromElement) {
        return tailSet(fromElement, true);
    }

    public Comparator<? super E> comparator() {
        return m.comparator();
    }
    public E first() {
        return m.firstKey();
    }
    public E last() {
        return m.lastKey();
    }

// NavigableSet API methods

    public E lower(E e) {
        return m.lowerKey(e);
    }

    public E floor(E e) {
        return m.floorKey(e);
    }
    public E ceiling(E e) {
        return m.ceilingKey(e);
    }
    public E higher(E e) {
        return m.higherKey(e);
    }
    public E pollFirst() {
        Map.Entry<E,?> e = m.pollFirstEntry();
        return (e == null) ? null : e.getKey();
    }
    public E pollLast() {
        Map.Entry<E,?> e = m.pollLastEntry();
        return (e == null) ? null : e.getKey();
    }
    public Object clone() {
        TreeSet<E> clone = null;
        try {
            clone = (TreeSet<E>) super.clone();
        } catch (CloneNotSupportedException e) {
            throw new InternalError();
        }

        clone.m = new TreeMap<>(m);
        return clone;
    }
    private void writeObject(java.io.ObjectOutputStream s)
        throws java.io.IOException {
        // Write out any hidden stuff
        s.defaultWriteObject();
        // Write out Comparator
        s.writeObject(m.comparator());
        // Write out size
        s.writeInt(m.size());
        // Write out all elements in the proper order.
        for (E e : m.keySet())
            s.writeObject(e);
    }
    private void readObject(java.io.ObjectInputStream s)
        throws java.io.IOException, ClassNotFoundException {
        // Read in any hidden stuff
        s.defaultReadObject();

        // Read in Comparator
        Comparator<? super E> c = (Comparator<? super E>) s.readObject();

        // Create backing TreeMap
        TreeMap<E,Object> tm;
        if (c==null)
            tm = new TreeMap<>();
        else
            tm = new TreeMap<>(c);
        m = tm;

        // Read in size
        int size = s.readInt();

        tm.readTreeSet(size, s, PRESENT);
    }

    private static final long serialVersionUID = -2479143000061671589L;
}