TreeSet 源代码
1、介绍TreeSet前先介绍它实现的接口NavigableSet
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* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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* Written by Doug Lea and Josh Bloch with assistance from members of JCP
* JSR-166 Expert Group and released to the public domain, as explained at
* http://creativecommons.org/publicdomain/zero/1.0/
*/
package java.util;
/**
* A {@link SortedSet} extended with navigation methods reporting
* closest matches for given search targets. Methods {@code lower},
* {@code floor}, {@code ceiling}, and {@code higher} return elements
* respectively less than, less than or equal, greater than or equal,
* and greater than a given element, returning {@code null} if there
* is no such element. A {@code NavigableSet} may be accessed and
* traversed in either ascending or descending order. The {@code
* descendingSet} method returns a view of the set with the senses of
* all relational and directional methods inverted. The performance of
* ascending operations and views is likely to be faster than that of
* descending ones. This interface additionally defines methods
* {@code pollFirst} and {@code pollLast} that return and remove the
* lowest and highest element, if one exists, else returning {@code
* null}. Methods {@code subSet}, {@code headSet},
* and {@code tailSet} differ from the like-named {@code
* SortedSet} methods in accepting additional arguments describing
* whether lower and upper bounds are inclusive versus exclusive.
* Subsets of any {@code NavigableSet} must implement the {@code
* NavigableSet} interface.
*
* <p> The return values of navigation methods may be ambiguous in
* implementations that permit {@code null} elements. However, even
* in this case the result can be disambiguated by checking
* {@code contains(null)}. To avoid such issues, implementations of
* this interface are encouraged to <em>not</em> permit insertion of
* {@code null} elements. (Note that sorted sets of {@link
* Comparable} elements intrinsically do not permit {@code null}.)
*
* <p>Methods
* {@link #subSet(Object, Object) subSet(E, E)},
* {@link #headSet(Object) headSet(E)}, and
* {@link #tailSet(Object) tailSet(E)}
* are specified to return {@code SortedSet} to allow existing
* implementations of {@code SortedSet} to be compatibly retrofitted to
* implement {@code NavigableSet}, but extensions and implementations
* of this interface are encouraged to override these methods to return
* {@code NavigableSet}.
*
* <p>This interface is a member of the
* <a href="{@docRoot}/../technotes/guides/collections/index.html">
* Java Collections Framework</a>.
*
* @author Doug Lea
* @author Josh Bloch
* @param <E> the type of elements maintained by this set
* @since 1.6
*/
/*
扩展的 SortedSet，具有了为给定搜索目标报告最接近匹配项的导航方法。方法 lower、floor、ceiling
和 higher 分别返回小于、小于等于、大于等于、大于给定元素的元素，如果不存在这样的元素，
则返回 null。可以按升序或降序访问和遍历 NavigableSet。descendingSet 方法返回 set 的一个视图，
该视图表示的所有关系方法和方向方法都是逆向的。升序操作和视图的性能很可能比降序操作和视图的性能要好。
此外，此接口还定义了 pollFirst 和 pollLast 方法，它们返回并移除最小和最大的元素（如果存在），
否则返回 null。subSet、headSet 和 tailSet 方法与名称相似的 SortedSet 方法的不同之处在于：
可以接受用于描述是否包括（或不包括）下边界和上边界的附加参数。任何 NavigableSet 的 Submap
必须实现 NavigableSet 接口。
导航方法的返回值在允许 null 元素的实现中可能是不确定的。不过，即使在这种情况下，也可以通过检查
contains(null) 来明确结果。为了避免这样的问题，建议在此接口的实现中不 允许插入 null 元素。
（注意，Comparable 元素的有序集本身不允许 null。）
subSet(E, E)、headSet(E) 和 tailSet(E) 方法被指定为返回 SortedSet，以允许现有 SortedSet
实现能相容地改进为实现 NavigableMap，但鼓励此接口的扩展和实现重写这些方法以返回 NavigableSet。
*/
public interface NavigableSet<E> extends SortedSet<E> {
/**
* Returns the greatest element in this set strictly less than the
* given element, or {@code null} if there is no such element.
*
* @param e the value to match
* @return the greatest element less than {@code e},
* or {@code null} if there is no such element
* @throws ClassCastException if the specified element cannot be
* compared with the elements currently in the set
* @throws NullPointerException if the specified element is null
* and this set does not permit null elements
*/
//返回小于e的元素
E lower(E e);
/**
* Returns the greatest element in this set less than or equal to
* the given element, or {@code null} if there is no such element.
*
* @param e the value to match
* @return the greatest element less than or equal to {@code e},
* or {@code null} if there is no such element
* @throws ClassCastException if the specified element cannot be
* compared with the elements currently in the set
* @throws NullPointerException if the specified element is null
* and this set does not permit null elements
*/
//返回小于或等于e的最大的元素
E floor(E e);
/**
* Returns the least element in this set greater than or equal to
* the given element, or {@code null} if there is no such element.
*
* @param e the value to match
* @return the least element greater than or equal to {@code e},
* or {@code null} if there is no such element
* @throws ClassCastException if the specified element cannot be
* compared with the elements currently in the set
* @throws NullPointerException if the specified element is null
* and this set does not permit null elements
*/
//返回大于或等于e的最小的元素
E ceiling(E e);
/**
* Returns the least element in this set strictly greater than the
* given element, or {@code null} if there is no such element.
*
* @param e the value to match
* @return the least element greater than {@code e},
* or {@code null} if there is no such element
* @throws ClassCastException if the specified element cannot be
* compared with the elements currently in the set
* @throws NullPointerException if the specified element is null
* and this set does not permit null elements
*/
//返回大于e的最小的元素
E higher(E e);
/**
* Retrieves and removes the first (lowest) element,
* or returns {@code null} if this set is empty.
*
* @return the first element, or {@code null} if this set is empty
*/
//返回并移除掉第一个元素，即为最小的元素
E pollFirst();
/**
* Retrieves and removes the last (highest) element,
* or returns {@code null} if this set is empty.
*
* @return the last element, or {@code null} if this set is empty
*/
//返回并移除掉最后一个元素，即为最大的元素
E pollLast();
/**
* Returns an iterator over the elements in this set, in ascending order.
*
* @return an iterator over the elements in this set, in ascending order
*/
//返回容器的迭代器
Iterator<E> iterator();
/**
* Returns a reverse order view of the elements contained in this set.
* The descending set is backed by this set, so changes to the set are
* reflected in the descending set, and vice-versa. If either set is
* modified while an iteration over either set is in progress (except
* through the iterator's own {@code remove} operation), the results of
* the iteration are undefined.
*
* <p>The returned set has an ordering equivalent to
* <tt>{@link Collections#reverseOrder(Comparator) Collections.reverseOrder}(comparator())</tt>.
* The expression {@code s.descendingSet().descendingSet()} returns a
* view of {@code s} essentially equivalent to {@code s}.
*
* @return a reverse order view of this set
*/
//返回逆序的Set
NavigableSet<E> descendingSet();
/**
* Returns an iterator over the elements in this set, in descending order.
* Equivalent in effect to {@code descendingSet().iterator()}.
*
* @return an iterator over the elements in this set, in descending order
*/
//返回逆序的迭代器
Iterator<E> descendingIterator();
/**
* Returns a view of the portion of this set whose elements range from
* {@code fromElement} to {@code toElement}. If {@code fromElement} and
* {@code toElement} are equal, the returned set is empty unless {@code
* fromInclusive} and {@code toInclusive} are both true. The returned set
* is backed by this set, so changes in the returned set are reflected in
* this set, and vice-versa. The returned set supports all optional set
* operations that this set supports.
*
* <p>The returned set will throw an {@code IllegalArgumentException}
* on an attempt to insert an element outside its range.
*
* @param fromElement low endpoint of the returned set
* @param fromInclusive {@code true} if the low endpoint
* is to be included in the returned view
* @param toElement high endpoint of the returned set
* @param toInclusive {@code true} if the high endpoint
* is to be included in the returned view
* @return a view of the portion of this set whose elements range from
* {@code fromElement}, inclusive, to {@code toElement}, exclusive
* @throws ClassCastException if {@code fromElement} and
* {@code toElement} 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 {@code fromElement} or
* {@code toElement} cannot be compared to elements currently in
* the set.
* @throws NullPointerException if {@code fromElement} or
* {@code toElement} is null and this set does
* not permit null elements
* @throws IllegalArgumentException if {@code fromElement} is
* greater than {@code toElement}; or if this set itself
* has a restricted range, and {@code fromElement} or
* {@code toElement} lies outside the bounds of the range.
*/
//返回子Set fromInclusive表示是否包含fromElement，toInclusive表示是否包含toElement
NavigableSet<E> subSet(E fromElement, boolean fromInclusive,
E toElement, boolean toInclusive);
/**
* Returns a view of the portion of this set whose elements are less than
* (or equal to, if {@code inclusive} is true) {@code toElement}. The
* returned set is backed by this set, so changes in the returned set are
* reflected in this set, and vice-versa. The returned set supports all
* optional set operations that this set supports.
*
* <p>The returned set will throw an {@code IllegalArgumentException}
* on an attempt to insert an element outside its range.
*
* @param toElement high endpoint of the returned set
* @param inclusive {@code true} if the high endpoint
* is to be included in the returned view
* @return a view of the portion of this set whose elements are less than
* (or equal to, if {@code inclusive} is true) {@code toElement}
* @throws ClassCastException if {@code toElement} is not compatible
* with this set's comparator (or, if the set has no comparator,
* if {@code toElement} does not implement {@link Comparable}).
* Implementations may, but are not required to, throw this
* exception if {@code toElement} cannot be compared to elements
* currently in the set.
* @throws NullPointerException if {@code toElement} is null and
* this set does not permit null elements
* @throws IllegalArgumentException if this set itself has a
* restricted range, and {@code toElement} lies outside the
* bounds of the range
*/
//返回子Set，
NavigableSet<E> headSet(E toElement, boolean inclusive);
/**
* Returns a view of the portion of this set whose elements are greater
* than (or equal to, if {@code inclusive} is true) {@code fromElement}.
* The returned set is backed by this set, so changes in the returned set
* are reflected in this set, and vice-versa. The returned set supports
* all optional set operations that this set supports.
*
* <p>The returned set will throw an {@code IllegalArgumentException}
* on an attempt to insert an element outside its range.
*
* @param fromElement low endpoint of the returned set
* @param inclusive {@code true} if the low endpoint
* is to be included in the returned view
* @return a view of the portion of this set whose elements are greater
* than or equal to {@code fromElement}
* @throws ClassCastException if {@code fromElement} is not compatible
* with this set's comparator (or, if the set has no comparator,
* if {@code fromElement} does not implement {@link Comparable}).
* Implementations may, but are not required to, throw this
* exception if {@code fromElement} cannot be compared to elements
* currently in the set.
* @throws NullPointerException if {@code fromElement} is null
* and this set does not permit null elements
* @throws IllegalArgumentException if this set itself has a
* restricted range, and {@code fromElement} lies outside the
* bounds of the range
*/
//返回子Set
NavigableSet<E> tailSet(E fromElement, boolean inclusive);
/**
* {@inheritDoc}
*
* <p>Equivalent to {@code subSet(fromElement, true, toElement, false)}.
*
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
* @throws IllegalArgumentException {@inheritDoc}
*/
//返回排序的子Set [fromElement, toElement)
SortedSet<E> subSet(E fromElement, E toElement);
/**
* {@inheritDoc}
*
* <p>Equivalent to {@code headSet(toElement, false)}.
*
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
* @throws IllegalArgumentException {@inheritDoc}
*/
//返回排序的子Set ( - , toElement)
SortedSet<E> headSet(E toElement);
/**
* {@inheritDoc}
*
* <p>Equivalent to {@code tailSet(fromElement, true)}.
*
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
* @throws IllegalArgumentException {@inheritDoc}
*/
//返回排序的子Set [fromElement , -)
SortedSet<E> tailSet(E fromElement);
}
2、TreeSet底层实现是NavigableMap，默认是TreeMap，很多方法都是调用底层的map对应的方法实现的
//底层是NavigableMap实现的，默认是TreeMap
private transient NavigableMap<E,Object> m;
// Dummy value to associate with an Object in the backing Map
//设置为value的对象
private static final Object PRESENT = new Object();
3、TreeSet源代码
/*
* Copyright (c) 1998, 2013, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package java.util;
/**
* A {@link NavigableSet} implementation based on a {@link TreeMap}.
* The elements are ordered using their {@linkplain Comparable natural
* ordering}, or by a {@link Comparator} provided at set creation
* time, depending on which constructor is used.
*
* <p>This implementation provides guaranteed log(n) time cost for the basic
* operations ({@code add}, {@code remove} and {@code contains}).
*
* <p>Note that the ordering maintained by a set (whether or not an explicit
* comparator is provided) must be <i>consistent with equals</i> if it is to
* correctly implement the {@code Set} interface. (See {@code Comparable}
* or {@code Comparator} for a precise definition of <i>consistent with
* equals</i>.) This is so because the {@code Set} interface is defined in
* terms of the {@code equals} operation, but a {@code TreeSet} instance
* performs all element comparisons using its {@code compareTo} (or
* {@code compare}) method, so two elements that are deemed equal by this method
* are, from the standpoint of the set, equal. The behavior of a set
* <i>is</i> well-defined even if its ordering is inconsistent with equals; it
* just fails to obey the general contract of the {@code Set} interface.
*
* <p><strong>Note that this implementation is not synchronized.</strong>
* If multiple threads access a tree set concurrently, and at least one
* of the threads modifies the set, it <i>must</i> be synchronized
* externally. This is typically accomplished by synchronizing on some
* object that naturally encapsulates the set.
* If no such object exists, the set should be "wrapped" using the
* {@link Collections#synchronizedSortedSet Collections.synchronizedSortedSet}
* method. This is best done at creation time, to prevent accidental
* unsynchronized access to the set: <pre>
* SortedSet s = Collections.synchronizedSortedSet(new TreeSet(...));</pre>
*
* <p>The iterators returned by this class's {@code iterator} method are
* <i>fail-fast</i>: if the set is modified at any time after the iterator is
* created, in any way except through the iterator's own {@code remove}
* method, the iterator will throw a {@link ConcurrentModificationException}.
* Thus, in the face of concurrent modification, the iterator fails quickly
* and cleanly, rather than risking arbitrary, non-deterministic behavior at
* an undetermined time in the future.
*
* <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
* as it is, generally speaking, impossible to make any hard guarantees in the
* presence of unsynchronized concurrent modification. Fail-fast iterators
* throw {@code ConcurrentModificationException} on a best-effort basis.
* Therefore, it would be wrong to write a program that depended on this
* exception for its correctness: <i>the fail-fast behavior of iterators
* should be used only to detect bugs.</i>
*
* <p>This class is a member of the
* <a href="{@docRoot}/../technotes/guides/collections/index.html">
* Java Collections Framework</a>.
*
* @param <E> the type of elements maintained by this set
*
* @author Josh Bloch
* @see Collection
* @see Set
* @see HashSet
* @see Comparable
* @see Comparator
* @see TreeMap
* @since 1.2
*/
/*
基于 TreeMap 的 NavigableSet 实现。使用元素的自然顺序对元素进行排序，
或者根据创建 set 时提供的 Comparator 进行排序，具体取决于使用的构造方法。
此实现为基本操作（add、remove 和 contains）提供受保证的 log(n) 时间开销。
注意，如果要正确实现 Set 接口，则 set 维护的顺序（无论是否提供了显式比较器）必须与 equals 一致。
（关于与 equals 一致 的精确定义，请参阅 Comparable 或 Comparator。）
这是因为 Set 接口是按照 equals 操作定义的，但 TreeSet 实例使用它的 compareTo（或 compare）
方法对所有元素进行比较，因此从 set 的观点来看，此方法认为相等的两个元素就是相等的。
即使 set 的顺序与 equals 不一致，其行为也是 定义良好的；它只是违背了 Set 接口的常规协定。
注意，此实现不是同步的。如果多个线程同时访问一个 TreeSet，而其中至少一个线程修改了该 set，
那么它必须 外部同步。这一般是通过对自然封装该 set 的对象执行同步操作来完成的。如果不存在这样的对象，
则应该使用 Collections.synchronizedSortedSet 方法来“包装”该 set。此操作最好在创建时进行，以防止对 set 的意外非同步访问：
SortedSet s = Collections.synchronizedSortedSet(new TreeSet(...));此类的 iterator
方法返回的迭代器是快速失败 的：在创建迭代器之后，如果从结构上对 set 进行修改，除非通过迭代器自身的 remove 方法，
否则在其他任何时间以任何方式进行修改都将导致迭代器抛出 ConcurrentModificationException。因此，对于并发的修改，
迭代器很快就完全失败，而不会冒着在将来不确定的时间发生不确定行为的风险。
注意，迭代器的快速失败行为无法得到保证，一般来说，存在不同步的并发修改时，不可能作出任何肯定的保证。
快速失败迭代器尽最大努力抛出 ConcurrentModificationException。因此，编写依赖于此异常的程序的做法是错误的，
正确做法是：迭代器的快速失败行为应该仅用于检测 bug。
*/
public class TreeSet<E> extends AbstractSet<E>
implements NavigableSet<E>, Cloneable, java.io.Serializable
{
/**
* The backing map.
*/
//底层是NavigableMap实现的，默认是TreeMap
private transient NavigableMap<E,Object> m;
// Dummy value to associate with an Object in the backing Map
//设置为value的对象
private static final Object PRESENT = new Object();
/**
* Constructs a set backed by the specified navigable map.
*/
//构造器，传入底层map
TreeSet(NavigableMap<E,Object> m) {
this.m = m;
}
/**
* Constructs a new, empty tree set, sorted according to the
* natural ordering of its elements. All elements inserted into
* the set must implement the {@link Comparable} interface.
* Furthermore, all such elements must be <i>mutually
* comparable</i>: {@code e1.compareTo(e2)} must not throw a
* {@code ClassCastException} for any elements {@code e1} and
* {@code e2} in the set. If the user attempts to add an element
* to the set that violates this constraint (for example, the user
* attempts to add a string element to a set whose elements are
* integers), the {@code add} call will throw a
* {@code ClassCastException}.
*/
//构造方法
public TreeSet() {
//默认底层map是TreeMap
this(new TreeMap<E,Object>());
}
/**
* Constructs a new, empty tree set, sorted according to the specified
* comparator. All elements inserted into the set must be <i>mutually
* comparable</i> by the specified comparator: {@code comparator.compare(e1,
* e2)} must not throw a {@code ClassCastException} for any elements
* {@code e1} and {@code e2} in the set. If the user attempts to add
* an element to the set that violates this constraint, the
* {@code add} call will throw a {@code ClassCastException}.
*
* @param comparator the comparator that will be used to order this set.
* If {@code null}, the {@linkplain Comparable natural
* ordering} of the elements will be used.
*/
//构造方法，传入比较器
public TreeSet(Comparator<? super E> comparator) {
this(new TreeMap<>(comparator));
}
/**
* Constructs a new tree set containing the elements in the specified
* collection, sorted according to the <i>natural ordering</i> of its
* elements. All elements inserted into the set must implement the
* {@link Comparable} interface. Furthermore, all such elements must be
* <i>mutually comparable</i>: {@code e1.compareTo(e2)} must not throw a
* {@code ClassCastException} for any elements {@code e1} and
* {@code e2} in the set.
*
* @param c collection whose elements will comprise the new set
* @throws ClassCastException if the elements in {@code c} are
* not {@link Comparable}, or are not mutually comparable
* @throws NullPointerException if the specified collection is null
*/
//构造方法，传入容器
public TreeSet(Collection<? extends E> c) {
this();
addAll(c);
}
/**
* Constructs a new tree set containing the same elements and
* using the same ordering as the specified sorted set.
*
* @param s sorted set whose elements will comprise the new set
* @throws NullPointerException if the specified sorted set is null
*/
//构造方法，传入排序的Set
public TreeSet(SortedSet<E> s) {
this(s.comparator());
addAll(s);
}
/**
* Returns an iterator over the elements in this set in ascending order.
*
* @return an iterator over the elements in this set in ascending order
*/
//返回迭代器
public Iterator<E> iterator() {
//调用底层的map，返回map中的key组成的set的迭代器
return m.navigableKeySet().iterator();
}
/**
* Returns an iterator over the elements in this set in descending order.
*
* @return an iterator over the elements in this set in descending order
* @since 1.6
*/
//返回逆序的迭代器
public Iterator<E> descendingIterator() {
//调用底层的map，返回map中的逆序的key组成的set的迭代器
return m.descendingKeySet().iterator();
}
/**
* @since 1.6
*/
//返回逆序的TreeSet
public NavigableSet<E> descendingSet() {
//调用底层的map，获取逆序的map后创建TreeSet
return new TreeSet<>(m.descendingMap());
}
/**
* Returns the number of elements in this set (its cardinality).
*
* @return the number of elements in this set (its cardinality)
*/
//获取TreeSet的容量
public int size() {
//调用底层map的size()
return m.size();
}
/**
* Returns {@code true} if this set contains no elements.
*
* @return {@code true} if this set contains no elements
*/
//判断是否为空
public boolean isEmpty() {
return m.isEmpty();
}
/**
* Returns {@code true} if this set contains the specified element.
* More formally, returns {@code true} if and only if this set
* contains an element {@code e} such that
* <tt>(o==null ? e==null : o.equals(e))</tt>.
*
* @param o object to be checked for containment in this set
* @return {@code true} if this set contains the specified element
* @throws ClassCastException if the specified object cannot be compared
* with the elements currently in the set
* @throws NullPointerException if the specified element is null
* and this set uses natural ordering, or its comparator
* does not permit null elements
*/
//判断是否包含对象o
public boolean contains(Object o) {
//调用底层map的containsKey
return m.containsKey(o);
}
/**
* Adds the specified element to this set if it is not already present.
* More formally, adds the specified element {@code e} to this set if
* the set contains no element {@code e2} such that
* <tt>(e==null ? e2==null : e.equals(e2))</tt>.
* If this set already contains the element, the call leaves the set
* unchanged and returns {@code false}.
*
* @param e element to be added to this set
* @return {@code true} if this set did not already contain the specified
* element
* @throws ClassCastException if the specified object cannot be compared
* with the elements currently in this set
* @throws NullPointerException if the specified element is null
* and this set uses natural ordering, or its comparator
* does not permit null elements
*/
//添加元素
public boolean add(E e) {
//将e设为key,PRESENT设为value
return m.put(e, PRESENT)==null;
}
/**
* Removes the specified element from this set if it is present.
* More formally, removes an element {@code e} such that
* <tt>(o==null ? e==null : o.equals(e))</tt>,
* if this set contains such an element. Returns {@code true} if
* this set contained the element (or equivalently, if this set
* changed as a result of the call). (This set will not contain the
* element once the call returns.)
*
* @param o object to be removed from this set, if present
* @return {@code true} if this set contained the specified element
* @throws ClassCastException if the specified object cannot be compared
* with the elements currently in this set
* @throws NullPointerException if the specified element is null
* and this set uses natural ordering, or its comparator
* does not permit null elements
*/
//移除调o
public boolean remove(Object o) {
return m.remove(o)==PRESENT;
}
/**
* Removes all of the elements from this set.
* The set will be empty after this call returns.
*/
//清除掉容器中的元素
public void clear() {
m.clear();
}
/**
* Adds all of the elements in the specified collection to this set.
*
* @param c collection containing elements to be added to this set
* @return {@code true} if this set changed as a result of the call
* @throws ClassCastException if the elements provided cannot be compared
* with the elements currently in the set
* @throws NullPointerException if the specified collection is null or
* if any element is null and this set uses natural ordering, or
* its comparator does not permit null elements
*/
//将容器e中的元素添加到TreeSet中
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<?> cc = set.comparator();
Comparator<? super E> mc = map.comparator();
if (cc==mc || (cc != null && cc.equals(mc))) {
//为TreeSet添加元素
map.addAllForTreeSet(set, PRESENT);
return true;
}
}
return super.addAll(c);
}
/**
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if {@code fromElement} or {@code toElement}
* is null and this set uses natural ordering, or its comparator
* does not permit null elements
* @throws IllegalArgumentException {@inheritDoc}
* @since 1.6
*/
//返回从fromElement 到 toElement 的元素
public NavigableSet<E> subSet(E fromElement, boolean fromInclusive,
E toElement, boolean toInclusive) {
//调用底层map的subMap方法
return new TreeSet<>(m.subMap(fromElement, fromInclusive,
toElement, toInclusive));
}
/**
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if {@code toElement} is null and
* this set uses natural ordering, or its comparator does
* not permit null elements
* @throws IllegalArgumentException {@inheritDoc}
* @since 1.6
*/
//返回比toElement小的元素，如果inclusive为true，则toElement也包含
public NavigableSet<E> headSet(E toElement, boolean inclusive) {
//调用底层map的方法
return new TreeSet<>(m.headMap(toElement, inclusive));
}
/**
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if {@code fromElement} is null and
* this set uses natural ordering, or its comparator does
* not permit null elements
* @throws IllegalArgumentException {@inheritDoc}
* @since 1.6
*/
//返回比fromElement大（inclusive==true,则fromElement包含）的元素
public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
//调用底层map的方法
return new TreeSet<>(m.tailMap(fromElement, inclusive));
}
/**
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if {@code fromElement} or
* {@code toElement} is null and this set uses natural ordering,
* or its comparator does not permit null elements
* @throws IllegalArgumentException {@inheritDoc}
*/
//返回[fromElement， toElement)的Set
public SortedSet<E> subSet(E fromElement, E toElement) {
return subSet(fromElement, true, toElement, false);
}
/**
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if {@code toElement} is null
* and this set uses natural ordering, or its comparator does
* not permit null elements
* @throws IllegalArgumentException {@inheritDoc}
*/
//返回比toElemeent小的元素组成的Set
public SortedSet<E> headSet(E toElement) {
return headSet(toElement, false);
}
/**
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if {@code fromElement} is null
* and this set uses natural ordering, or its comparator does
* not permit null elements
* @throws IllegalArgumentException {@inheritDoc}
*/
//返回大于等于fromElement的元素组成的Set
public SortedSet<E> tailSet(E fromElement) {
return tailSet(fromElement, true);
}
public Comparator<? super E> comparator() {
//返回比较器
return m.comparator();
}
/**
* @throws NoSuchElementException {@inheritDoc}
*/
//返回第一个元素，即最小的元素
public E first() {
return m.firstKey();
}
/**
* @throws NoSuchElementException {@inheritDoc}
*/
//返回最后一个元素，即最大的元素
public E last() {
return m.lastKey();
}
// NavigableSet API methods
/**
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if the specified element is null
* and this set uses natural ordering, or its comparator
* does not permit null elements
* @since 1.6
*/
//返回比e小的最大的元素
public E lower(E e) {
return m.lowerKey(e);
}
/**
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if the specified element is null
* and this set uses natural ordering, or its comparator
* does not permit null elements
* @since 1.6
*/
//返回小于等于e的最大的元素
public E floor(E e) {
return m.floorKey(e);
}
/**
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if the specified element is null
* and this set uses natural ordering, or its comparator
* does not permit null elements
* @since 1.6
*/
//返回大于等于e的最小的元素
public E ceiling(E e) {
return m.ceilingKey(e);
}
/**
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if the specified element is null
* and this set uses natural ordering, or its comparator
* does not permit null elements
* @since 1.6
*/
//返回大于e的最小的元素
public E higher(E e) {
return m.higherKey(e);
}
/**
* @since 1.6
*/
//返回并移除掉第一个元素
public E pollFirst() {
Map.Entry<E,?> e = m.pollFirstEntry();
return (e == null) ? null : e.getKey();
}
/**
* @since 1.6
*/
//返回并移除掉最后一个元素
public E pollLast() {
Map.Entry<E,?> e = m.pollLastEntry();
return (e == null) ? null : e.getKey();
}
/**
* Returns a shallow copy of this {@code TreeSet} instance. (The elements
* themselves are not cloned.)
*
* @return a shallow copy of this set
*/
//克隆
@SuppressWarnings("unchecked")
public Object clone() {
TreeSet<E> clone;
try {
clone = (TreeSet<E>) super.clone();
} catch (CloneNotSupportedException e) {
throw new InternalError(e);
}
clone.m = new TreeMap<>(m);
return clone;
}
/**
* Save the state of the {@code TreeSet} instance to a stream (that is,
* serialize it).
*
* @serialData Emits the comparator used to order this set, or
* {@code null} if it obeys its elements' natural ordering
* (Object), followed by the size of the set (the number of
* elements it contains) (int), followed by all of its
* elements (each an Object) in order (as determined by the
* set's Comparator, or by the elements' natural ordering if
* the set has no Comparator).
*/
//用于序列化的writeObject
private void writeObject(java.io.ObjectOutputStream s)
throws java.io.IOException {
// Write out any hidden stuff
s.defaultWriteObject();
// Write out Comparator
//先写构造器
s.writeObject(m.comparator());
// Write out size
//再写大小
s.writeInt(m.size());
// Write out all elements in the proper order.
//后写元素
for (E e : m.keySet())
s.writeObject(e);
}
/**
* Reconstitute the {@code TreeSet} instance from a stream (that is,
* deserialize it).
*/
//用于序列化的readObject
private void readObject(java.io.ObjectInputStream s)
throws java.io.IOException, ClassNotFoundException {
// Read in any hidden stuff
s.defaultReadObject();
// Read in Comparator
//先读取比较器
@SuppressWarnings("unchecked")
Comparator<? super E> c = (Comparator<? super E>) s.readObject();
// Create backing TreeMap
//创建底层的TreeMap
TreeMap<E,Object> tm = new TreeMap<>(c);
m = tm;
// Read in size
//读取大小
int size = s.readInt();
//初始化TreeSet
tm.readTreeSet(size, s, PRESENT);
}
/**
* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
* and <em>fail-fast</em> {@link Spliterator} over the elements in this
* set.
*
* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
* {@link Spliterator#DISTINCT}, {@link Spliterator#SORTED}, and
* {@link Spliterator#ORDERED}. Overriding implementations should document
* the reporting of additional characteristic values.
*
* <p>The spliterator's comparator (see
* {@link java.util.Spliterator#getComparator()}) is {@code null} if
* the tree set's comparator (see {@link #comparator()}) is {@code null}.
* Otherwise, the spliterator's comparator is the same as or imposes the
* same total ordering as the tree set's comparator.
*
* @return a {@code Spliterator} over the elements in this set
* @since 1.8
*/
public Spliterator<E> spliterator() {
return TreeMap.keySpliteratorFor(m);
}
private static final long serialVersionUID = -2479143000061671589L;
}