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[Java教程]java集合类分析


//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;}