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/* |
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* %W% %E% |
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* |
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* Copyright 2004 Sun Microsystems, Inc. All rights reserved. |
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* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. |
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*/ |
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|
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package java.util; |
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|
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/** |
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* This class implements the <tt>Set</tt> interface, backed by a |
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* <tt>TreeMap</tt> instance. This class guarantees that the sorted set will |
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* be in ascending element order, sorted according to the <i>natural order</i> |
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* of the elements (see <tt>Comparable</tt>), or by the comparator provided at |
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* set creation time, depending on which constructor is used.<p> |
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* |
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* This implementation provides guaranteed log(n) time cost for the basic |
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* operations (<tt>add</tt>, <tt>remove</tt> and <tt>contains</tt>).<p> |
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* |
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* Note that the ordering maintained by a set (whether or not an explicit |
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* comparator is provided) must be <i>consistent with equals</i> if it is to |
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* correctly implement the <tt>Set</tt> interface. (See <tt>Comparable</tt> |
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* or <tt>Comparator</tt> for a precise definition of <i>consistent with |
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* equals</i>.) This is so because the <tt>Set</tt> interface is defined in |
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* terms of the <tt>equals</tt> operation, but a <tt>TreeSet</tt> instance |
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* performs all key comparisons using its <tt>compareTo</tt> (or |
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* <tt>compare</tt>) method, so two keys that are deemed equal by this method |
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* are, from the standpoint of the set, equal. The behavior of a set |
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* <i>is</i> well-defined even if its ordering is inconsistent with equals; it |
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* just fails to obey the general contract of the <tt>Set</tt> interface.<p> |
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* |
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* <b>Note that this implementation is not synchronized.</b> If multiple |
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* threads access a set concurrently, and at least one of the threads modifies |
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* the set, it <i>must</i> be synchronized externally. This is typically |
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* accomplished by synchronizing on some object that naturally encapsulates |
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* the set. If no such object exists, the set should be "wrapped" using the |
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* <tt>Collections.synchronizedSet</tt> method. This is best done at creation |
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* time, to prevent accidental unsynchronized access to the set: <pre> |
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* SortedSet s = Collections.synchronizedSortedSet(new TreeSet(...)); |
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* </pre><p> |
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* |
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* The Iterators returned by this class's <tt>iterator</tt> method are |
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* <i>fail-fast</i>: if the set is modified at any time after the iterator is |
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* created, in any way except through the iterator's own <tt>remove</tt> |
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* method, the iterator will throw a <tt>ConcurrentModificationException</tt>. |
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* Thus, in the face of concurrent modification, the iterator fails quickly |
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* and cleanly, rather than risking arbitrary, non-deterministic behavior at |
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* an undetermined time in the future. |
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* |
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* <p>Note that the fail-fast behavior of an iterator cannot be guaranteed |
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* as it is, generally speaking, impossible to make any hard guarantees in the |
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* presence of unsynchronized concurrent modification. Fail-fast iterators |
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* throw <tt>ConcurrentModificationException</tt> on a best-effort basis. |
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* Therefore, it would be wrong to write a program that depended on this |
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* exception for its correctness: <i>the fail-fast behavior of iterators |
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* should be used only to detect bugs.</i><p> |
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* |
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* This class is a member of the |
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* <a href="{@docRoot}/../guide/collections/index.html"> |
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* Java Collections Framework</a>. |
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* |
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* @author Josh Bloch |
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* @version %I%, %G% |
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* @see Collection |
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* @see Set |
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* @see HashSet |
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* @see Comparable |
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* @see Comparator |
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* @see Collections#synchronizedSortedSet(SortedSet) |
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* @see TreeMap |
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* @since 1.2 |
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*/ |
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|
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public class TreeSet<E> |
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extends AbstractSet<E> |
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implements NavigableSet<E>, Cloneable, java.io.Serializable |
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{ |
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private transient NavigableMap<E,Object> m; // The backing Map |
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|
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// Dummy value to associate with an Object in the backing Map |
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private static final Object PRESENT = new Object(); |
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|
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/** |
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* Constructs a set backed by the specified sorted map. |
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*/ |
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private TreeSet(NavigableMap<E,Object> m) { |
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this.m = m; |
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} |
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|
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/** |
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* Constructs a new, empty set, sorted according to the elements' natural |
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* order. All elements inserted into the set must implement the |
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* <tt>Comparable</tt> interface. Furthermore, all such elements must be |
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* <i>mutually comparable</i>: <tt>e1.compareTo(e2)</tt> must not throw a |
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* <tt>ClassCastException</tt> for any elements <tt>e1</tt> and |
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* <tt>e2</tt> in the set. If the user attempts to add an element to the |
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* set that violates this constraint (for example, the user attempts to |
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* add a string element to a set whose elements are integers), the |
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* <tt>add(Object)</tt> call will throw a <tt>ClassCastException</tt>. |
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* |
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* @see Comparable |
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*/ |
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public TreeSet() { |
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this(new TreeMap<E,Object>()); |
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} |
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|
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/** |
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* Constructs a new, empty set, sorted according to the specified |
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* comparator. All elements inserted into the set must be <i>mutually |
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* comparable</i> by the specified comparator: <tt>comparator.compare(e1, |
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* e2)</tt> must not throw a <tt>ClassCastException</tt> for any elements |
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* <tt>e1</tt> and <tt>e2</tt> in the set. If the user attempts to add |
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* an element to the set that violates this constraint, the |
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* <tt>add(Object)</tt> call will throw a <tt>ClassCastException</tt>. |
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* |
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* @param c the comparator that will be used to sort this set. A |
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* <tt>null</tt> value indicates that the elements' <i>natural |
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* ordering</i> should be used. |
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*/ |
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public TreeSet(Comparator<? super E> c) { |
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this(new TreeMap<E,Object>(c)); |
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} |
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|
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/** |
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* Constructs a new set containing the elements in the specified |
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* collection, sorted according to the elements' <i>natural order</i>. |
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* All keys inserted into the set must implement the <tt>Comparable</tt> |
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* interface. Furthermore, all such keys must be <i>mutually |
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* comparable</i>: <tt>k1.compareTo(k2)</tt> must not throw a |
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* <tt>ClassCastException</tt> for any elements <tt>k1</tt> and |
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* <tt>k2</tt> in the set. |
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* |
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* @param c The elements that will comprise the new set. |
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* |
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* @throws ClassCastException if the keys in the specified collection are |
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* not comparable, or are not mutually comparable. |
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* @throws NullPointerException if the specified collection is null. |
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*/ |
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public TreeSet(Collection<? extends E> c) { |
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this(); |
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addAll(c); |
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} |
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|
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/** |
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* Constructs a new set containing the same elements as the specified |
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* sorted set, sorted according to the same ordering. |
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* |
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* @param s sorted set whose elements will comprise the new set. |
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* @throws NullPointerException if the specified sorted set is null. |
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*/ |
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public TreeSet(SortedSet<E> s) { |
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this(s.comparator()); |
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addAll(s); |
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} |
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|
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/** |
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* Returns an iterator over the elements in this set. The elements |
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* are returned in ascending order. |
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* |
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* @return an iterator over the elements in this set. |
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*/ |
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public Iterator<E> iterator() { |
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return m.keySet().iterator(); |
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} |
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|
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/** |
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* Returns an iterator over the elements in this set. The elements |
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* are returned in descending order. |
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* |
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* @return an iterator over the elements in this set. |
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*/ |
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public Iterator<E> descendingIterator() { |
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return m.descendingKeySet().iterator(); |
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} |
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|
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/** |
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* Returns the number of elements in this set (its cardinality). |
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* |
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* @return the number of elements in this set (its cardinality). |
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*/ |
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public int size() { |
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return m.size(); |
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} |
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|
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/** |
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* Returns <tt>true</tt> if this set contains no elements. |
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* |
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* @return <tt>true</tt> if this set contains no elements. |
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*/ |
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public boolean isEmpty() { |
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return m.isEmpty(); |
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} |
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|
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/** |
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* Returns <tt>true</tt> if this set contains the specified element. |
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* |
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* @param o the object to be checked for containment in this set. |
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* @return <tt>true</tt> if this set contains the specified element. |
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* |
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* @throws ClassCastException if the specified object cannot be compared |
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* with the elements currently in the set. |
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* @throws NullPointerException if o is <tt>null</tt> and this map |
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* uses natural ordering and is non-empty, or its comparator does |
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* not tolerate <tt>null</tt> keys. |
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*/ |
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public boolean contains(Object o) { |
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return m.containsKey(o); |
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} |
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|
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/** |
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* Adds the specified element to this set if it is not already present. |
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* |
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* @param o element to be added to this set. |
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* @return <tt>true</tt> if the set did not already contain the specified |
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* element. |
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* |
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* @throws ClassCastException if the specified object cannot be compared |
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* with the elements currently in the set. |
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* @throws NullPointerException if o is <tt>null</tt> and this map |
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* uses natural ordering and is non-empty, or its comparator does |
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* not tolerate <tt>null</tt> keys. |
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*/ |
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public boolean add(E o) { |
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return m.put(o, PRESENT)==null; |
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} |
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|
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/** |
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* Removes the specified element from this set if it is present. |
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* |
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* @param o object to be removed from this set, if present. |
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* @return <tt>true</tt> if the set contained the specified element. |
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* |
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* @throws ClassCastException if the specified object cannot be compared |
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* with the elements currently in the set. |
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* @throws NullPointerException if o is <tt>null</tt> and this map |
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* uses natural ordering and is non-empty, or its comparator does |
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* not tolerate <tt>null</tt> keys. |
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*/ |
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public boolean remove(Object o) { |
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return m.remove(o)==PRESENT; |
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} |
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|
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/** |
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* Removes all of the elements from this set. |
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*/ |
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public void clear() { |
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m.clear(); |
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} |
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|
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/** |
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* Adds all of the elements in the specified collection to this set. |
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* |
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* @param c elements to be added |
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* @return <tt>true</tt> if this set changed as a result of the call. |
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* |
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* @throws ClassCastException if the elements provided cannot be compared |
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* with the elements currently in the set. |
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* @throws NullPointerException of the specified collection is |
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* <tt>null</tt> or if any element is <tt>null</tt> and this map |
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* uses natural ordering, or its comparator does not tolerate |
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* <tt>null</tt> keys. |
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*/ |
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public boolean addAll(Collection<? extends E> c) { |
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// Use linear-time version if applicable |
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if (m.size()==0 && c.size() > 0 && |
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c instanceof SortedSet && |
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m instanceof TreeMap) { |
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SortedSet<Map.Entry<E, Object>> set = (SortedSet<Map.Entry<E, Object>>) (SortedSet) c; |
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TreeMap<E,Object> map = (TreeMap<E, Object>) m; |
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Comparator<? super E> cc = (Comparator<E>) set.comparator(); |
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Comparator<? super E> mc = map.comparator(); |
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if (cc==mc || (cc != null && cc.equals(mc))) { |
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map.addAllForTreeSet(set, PRESENT); |
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return true; |
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} |
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} |
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return super.addAll(c); |
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} |
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|
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/** |
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* Returns a view of the portion of this set whose elements range from |
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* <tt>fromElement</tt>, inclusive, to <tt>toElement</tt>, exclusive. (If |
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* <tt>fromElement</tt> and <tt>toElement</tt> are equal, the returned |
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* sorted set is empty.) The returned sorted set is backed by this set, |
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* so changes in the returned sorted set are reflected in this set, and |
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* vice-versa. The returned sorted set supports all optional Set |
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* operations.<p> |
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* |
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* The sorted set returned by this method will throw an |
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* <tt>IllegalArgumentException</tt> if the user attempts to insert an |
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* element outside the specified range.<p> |
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* |
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* Note: this method always returns a <i>half-open range</i> (which |
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* includes its low endpoint but not its high endpoint). If you need a |
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* <i>closed range</i> (which includes both endpoints), and the element |
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* type allows for calculation of the successor of a specified value, |
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* merely request the subrange from <tt>lowEndpoint</tt> to |
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* <tt>successor(highEndpoint)</tt>. For example, suppose that <tt>s</tt> |
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* is a sorted set of strings. The following idiom obtains a view |
300 |
* containing all of the strings in <tt>s</tt> from <tt>low</tt> to |
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* <tt>high</tt>, inclusive: <pre> |
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* NavigableSet sub = s.subSet(low, high+"\0"); |
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* </pre> |
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* |
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* A similar technique can be used to generate an <i>open range</i> (which |
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* contains neither endpoint). The following idiom obtains a view |
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* containing all of the strings in <tt>s</tt> from <tt>low</tt> to |
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* <tt>high</tt>, exclusive: <pre> |
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* NavigableSet sub = s.subSet(low+"\0", high); |
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* </pre> |
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* |
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* @param fromElement low endpoint (inclusive) of the subSet. |
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* @param toElement high endpoint (exclusive) of the subSet. |
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* @return a view of the portion of this set whose elements range from |
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* <tt>fromElement</tt>, inclusive, to <tt>toElement</tt>, |
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* exclusive. |
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* @throws ClassCastException if <tt>fromElement</tt> and |
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* <tt>toElement</tt> cannot be compared to one another using |
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* this set's comparator (or, if the set has no comparator, |
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* using natural ordering). |
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* @throws IllegalArgumentException if <tt>fromElement</tt> is greater than |
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* <tt>toElement</tt>. |
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* @throws NullPointerException if <tt>fromElement</tt> or |
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* <tt>toElement</tt> is <tt>null</tt> and this set uses natural |
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* order, or its comparator does not tolerate <tt>null</tt> |
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* elements. |
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*/ |
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public NavigableSet<E> subSet(E fromElement, E toElement) { |
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return new TreeSet<E>(m.subMap(fromElement, toElement)); |
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} |
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|
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/** |
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* Returns a view of the portion of this set whose elements are strictly |
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* less than <tt>toElement</tt>. The returned sorted set is backed by |
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* this set, so changes in the returned sorted set are reflected in this |
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* set, and vice-versa. The returned sorted set supports all optional set |
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* operations.<p> |
338 |
* |
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* The sorted set returned by this method will throw an |
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* <tt>IllegalArgumentException</tt> if the user attempts to insert an |
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* element greater than or equal to <tt>toElement</tt>.<p> |
342 |
* |
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* Note: this method always returns a view that does not contain its |
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* (high) endpoint. If you need a view that does contain this endpoint, |
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* and the element type allows for calculation of the successor of a |
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* specified value, merely request a headSet bounded by |
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* <tt>successor(highEndpoint)</tt>. For example, suppose that <tt>s</tt> |
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* is a sorted set of strings. The following idiom obtains a view |
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* containing all of the strings in <tt>s</tt> that are less than or equal |
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* to <tt>high</tt>: <pre> NavigableSet head = s.headSet(high+"\0");</pre> |
351 |
* |
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* @param toElement high endpoint (exclusive) of the headSet. |
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* @return a view of the portion of this set whose elements are strictly |
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* less than toElement. |
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* @throws ClassCastException if <tt>toElement</tt> is not compatible |
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* with this set's comparator (or, if the set has no comparator, |
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* if <tt>toElement</tt> does not implement <tt>Comparable</tt>). |
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* @throws IllegalArgumentException if this set is itself a subSet, |
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* headSet, or tailSet, and <tt>toElement</tt> is not within the |
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* specified range of the subSet, headSet, or tailSet. |
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* @throws NullPointerException if <tt>toElement</tt> is <tt>null</tt> and |
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* this set uses natural ordering, or its comparator does |
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* not tolerate <tt>null</tt> elements. |
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*/ |
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public NavigableSet<E> headSet(E toElement) { |
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return new TreeSet<E>(m.headMap(toElement)); |
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} |
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|
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/** |
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* Returns a view of the portion of this set whose elements are |
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* greater than or equal to <tt>fromElement</tt>. The returned sorted set |
372 |
* is backed by this set, so changes in the returned sorted set are |
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* reflected in this set, and vice-versa. The returned sorted set |
374 |
* supports all optional set operations.<p> |
375 |
* |
376 |
* The sorted set returned by this method will throw an |
377 |
* <tt>IllegalArgumentException</tt> if the user attempts to insert an |
378 |
* element less than <tt>fromElement</tt>. |
379 |
* |
380 |
* Note: this method always returns a view that contains its (low) |
381 |
* endpoint. If you need a view that does not contain this endpoint, and |
382 |
* the element type allows for calculation of the successor of a specified |
383 |
* value, merely request a tailSet bounded by |
384 |
* <tt>successor(lowEndpoint)</tt>. For example, suppose that <tt>s</tt> |
385 |
* is a sorted set of strings. The following idiom obtains a view |
386 |
* containing all of the strings in <tt>s</tt> that are strictly greater |
387 |
* than <tt>low</tt>: <pre> |
388 |
* NavigableSet tail = s.tailSet(low+"\0"); |
389 |
* </pre> |
390 |
* |
391 |
* @param fromElement low endpoint (inclusive) of the tailSet. |
392 |
* @return a view of the portion of this set whose elements are |
393 |
* greater than or equal to <tt>fromElement</tt>. |
394 |
* @throws ClassCastException if <tt>fromElement</tt> is not compatible |
395 |
* with this set's comparator (or, if the set has no comparator, |
396 |
* if <tt>fromElement</tt> does not implement <tt>Comparable</tt>). |
397 |
* @throws IllegalArgumentException if this set is itself a subSet, |
398 |
* headSet, or tailSet, and <tt>fromElement</tt> is not within the |
399 |
* specified range of the subSet, headSet, or tailSet. |
400 |
* @throws NullPointerException if <tt>fromElement</tt> is <tt>null</tt> |
401 |
* and this set uses natural ordering, or its comparator does |
402 |
* not tolerate <tt>null</tt> elements. |
403 |
*/ |
404 |
public NavigableSet<E> tailSet(E fromElement) { |
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return new TreeSet<E>(m.tailMap(fromElement)); |
406 |
} |
407 |
|
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/** |
409 |
* Returns the comparator used to order this sorted set, or <tt>null</tt> |
410 |
* if this tree set uses its elements natural ordering. |
411 |
* |
412 |
* @return the comparator used to order this sorted set, or <tt>null</tt> |
413 |
* if this tree set uses its elements natural ordering. |
414 |
*/ |
415 |
public Comparator<? super E> comparator() { |
416 |
return m.comparator(); |
417 |
} |
418 |
|
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/** |
420 |
* Returns the first (lowest) element currently in this sorted set. |
421 |
* |
422 |
* @return the first (lowest) element currently in this sorted set. |
423 |
* @throws NoSuchElementException sorted set is empty. |
424 |
*/ |
425 |
public E first() { |
426 |
return m.firstKey(); |
427 |
} |
428 |
|
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/** |
430 |
* Returns the last (highest) element currently in this sorted set. |
431 |
* |
432 |
* @return the last (highest) element currently in this sorted set. |
433 |
* @throws NoSuchElementException sorted set is empty. |
434 |
*/ |
435 |
public E last() { |
436 |
return m.lastKey(); |
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} |
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|
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// NavigableSet API methods |
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|
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|
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/** |
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* Returns an element greater than or equal to the given element, or |
444 |
* <tt>null</tt> if there is no such element. |
445 |
* |
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* @param o the value to match |
447 |
* @return an element greater than or equal to given element, or |
448 |
* <tt>null</tt> if there is no such element. |
449 |
* @throws ClassCastException if o cannot be compared with the elements |
450 |
* currently in the set. |
451 |
* @throws NullPointerException if o is <tt>null</tt> and this map |
452 |
* uses natural ordering and is non-empty, or its comparator does |
453 |
* not tolerate <tt>null</tt> keys. |
454 |
*/ |
455 |
public E ceiling(E o) { |
456 |
return m.ceilingKey(o); |
457 |
} |
458 |
|
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/** |
460 |
* Returns an element strictly less than the given element, or |
461 |
* <tt>null</tt> if there is no such element. |
462 |
* |
463 |
* @param o the value to match |
464 |
* @return the greatest element less than the given element, or |
465 |
* <tt>null</tt> if there is no such element. |
466 |
* @throws ClassCastException if o cannot be compared with the elements |
467 |
* currently in the set. |
468 |
* @throws NullPointerException if o is <tt>null</tt> and this map |
469 |
* uses natural ordering and is non-empty, or its comparator does |
470 |
* not tolerate <tt>null</tt> keys. |
471 |
*/ |
472 |
public E lower(E o) { |
473 |
return m.lowerKey(o); |
474 |
} |
475 |
|
476 |
/** |
477 |
* Returns an element less than or equal to the given element, or |
478 |
* <tt>null</tt> if there is no such element. |
479 |
* |
480 |
* @param o the value to match |
481 |
* @return the greatest element less than or equal to given |
482 |
* element, or <tt>null</tt> if there is no such element. |
483 |
* @throws ClassCastException if o cannot be compared with the elements |
484 |
* currently in the set. |
485 |
* @throws NullPointerException if o is <tt>null</tt> and this map |
486 |
* uses natural ordering and is non-empty, or its comparator does |
487 |
* not tolerate <tt>null</tt> keys. |
488 |
*/ |
489 |
public E floor(E o) { |
490 |
return m.floorKey(o); |
491 |
} |
492 |
|
493 |
/** |
494 |
* Returns an element strictly greater than the given element, or |
495 |
* <tt>null</tt> if there is no such element. |
496 |
* |
497 |
* @param o the value to match |
498 |
* @return the least element greater than the given element, or |
499 |
* <tt>null</tt> if there is no such element. |
500 |
* @throws ClassCastException if o cannot be compared with the elements |
501 |
* currently in the set. |
502 |
* @throws NullPointerException if o is <tt>null</tt> and this map |
503 |
* uses natural ordering and is non-empty, or its comparator does |
504 |
* not tolerate <tt>null</tt> keys. |
505 |
*/ |
506 |
public E higher(E o) { |
507 |
return m.higherKey(o); |
508 |
} |
509 |
|
510 |
/** |
511 |
* Retrieves and removes the first (lowest) element. |
512 |
* |
513 |
* @return the least element, or <tt>null</tt> if empty. |
514 |
*/ |
515 |
public E pollFirst() { |
516 |
Map.Entry<E,?> e = m.pollFirstEntry(); |
517 |
return (e == null)? null : e.getKey(); |
518 |
} |
519 |
|
520 |
/** |
521 |
* Retrieves and removes the last (highest) element. |
522 |
* |
523 |
* @return the last element, or <tt>null</tt> if empty. |
524 |
*/ |
525 |
public E pollLast() { |
526 |
Map.Entry<E,?> e = m.pollLastEntry(); |
527 |
return (e == null)? null : e.getKey(); |
528 |
} |
529 |
|
530 |
/** |
531 |
* Returns a shallow copy of this <tt>TreeSet</tt> instance. (The elements |
532 |
* themselves are not cloned.) |
533 |
* |
534 |
* @return a shallow copy of this set. |
535 |
*/ |
536 |
public Object clone() { |
537 |
TreeSet<E> clone = null; |
538 |
try { |
539 |
clone = (TreeSet<E>) super.clone(); |
540 |
} catch (CloneNotSupportedException e) { |
541 |
throw new InternalError(); |
542 |
} |
543 |
|
544 |
clone.m = new TreeMap<E,Object>(m); |
545 |
|
546 |
return clone; |
547 |
} |
548 |
|
549 |
/** |
550 |
* Save the state of the <tt>TreeSet</tt> instance to a stream (that is, |
551 |
* serialize it). |
552 |
* |
553 |
* @serialData Emits the comparator used to order this set, or |
554 |
* <tt>null</tt> if it obeys its elements' natural ordering |
555 |
* (Object), followed by the size of the set (the number of |
556 |
* elements it contains) (int), followed by all of its |
557 |
* elements (each an Object) in order (as determined by the |
558 |
* set's Comparator, or by the elements' natural ordering if |
559 |
* the set has no Comparator). |
560 |
*/ |
561 |
private void writeObject(java.io.ObjectOutputStream s) |
562 |
throws java.io.IOException { |
563 |
// Write out any hidden stuff |
564 |
s.defaultWriteObject(); |
565 |
|
566 |
// Write out Comparator |
567 |
s.writeObject(m.comparator()); |
568 |
|
569 |
// Write out size |
570 |
s.writeInt(m.size()); |
571 |
|
572 |
// Write out all elements in the proper order. |
573 |
for (Iterator i=m.keySet().iterator(); i.hasNext(); ) |
574 |
s.writeObject(i.next()); |
575 |
} |
576 |
|
577 |
/** |
578 |
* Reconstitute the <tt>TreeSet</tt> instance from a stream (that is, |
579 |
* deserialize it). |
580 |
*/ |
581 |
private void readObject(java.io.ObjectInputStream s) |
582 |
throws java.io.IOException, ClassNotFoundException { |
583 |
// Read in any hidden stuff |
584 |
s.defaultReadObject(); |
585 |
|
586 |
// Read in Comparator |
587 |
Comparator<E> c = (Comparator<E>) s.readObject(); |
588 |
|
589 |
// Create backing TreeMap |
590 |
TreeMap<E,Object> tm; |
591 |
if (c==null) |
592 |
tm = new TreeMap<E,Object>(); |
593 |
else |
594 |
tm = new TreeMap<E,Object>(c); |
595 |
m = tm; |
596 |
|
597 |
// Read in size |
598 |
int size = s.readInt(); |
599 |
|
600 |
tm.readTreeSet(size, s, PRESENT); |
601 |
} |
602 |
|
603 |
private static final long serialVersionUID = -2479143000061671589L; |
604 |
} |