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Class com.sun.java.util.collections.TreeSet
java.lang.Object
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+----com.sun.java.util.collections.AbstractCollection
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+----com.sun.java.util.collections.AbstractSet
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+----com.sun.java.util.collections.TreeSet
- public class TreeSet
- extends AbstractSet
- implements SortedSet, Cloneable, Serializable
This class implements the Set interface, backed by a
TreeMap instance. This class guarantees that the sorted set will
be in ascending element order, sorted according to the natural order
of the elements (see Comparable), or by the comparator provided at
set creation time, depending on which constructor is used.
This implementation provides guaranteed log(n) time cost for the basic
operations (add, remove and contains).
Note that the ordering maintained by a set (whether or not an explicit
comparator is provided) must be consistent with equals if it is to
correctly implement the Set interface. (See Comparable
or Comparator for a precise definition of consistent with
equals.) This is so because the Set interface is defined in
terms of the equals operation, but a TreeSet instance
performs all key comparisons using its compareTo (or
compare) method, so two keys that are deemed equal by this method
are, from the standpoint of the set, equal. The behavior of a set
is well-defined even if its ordering is inconsistent with equals; it
just fails to obey the general contract of the Set interface.
Note that this implementation is not synchronized. If multiple
threads access a set concurrently, and at least one of the threads modifies
the set, it must 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
Collections.synchronizedSet method. This is best done at creation
time, to prevent accidental unsynchronized access to the set:
SortedSet s = Collections.synchronizedSortedSet(new TreeSet(...));
The Iterators returned by this class's iterator method are
fail-fast: if the set is modified at any time after the iterator is
created, in any way except through the iterator's own remove
method, the iterator will throw a 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.
- See Also:
- Collection, Set, HashSet, Comparable, Comparator, synchronizedSortedSet, TreeMap
-
TreeSet()
- Constructs a new, empty set, sorted according to the elements' natural
order.
-
TreeSet(Collection)
- Constructs a new set containing the elements in the specified
collection, sorted according to the elements' natural order.
-
TreeSet(Comparator)
- Constructs a new, empty set, sorted according to the given comparator.
-
TreeSet(SortedSet)
- Constructs a new set containing the same elements as the given sorted
set, sorted according to the same ordering.
-
add(Object)
- Adds the specified element to this set if it is not already present.
-
addAll(Collection)
- Adds all of the elements in the specified collection to this set.
-
clear()
- Removes all of the elements from this set.
-
clone()
- Returns a shallow copy of this TreeSet instance.
-
comparator()
- Returns the comparator used to order this sorted set, or null
if this tree map uses its keys natural ordering.
-
contains(Object)
- Returns true if this set contains the specified element.
-
first()
- Returns the first (lowest) element currently in this sorted set.
-
headSet(Object)
- Returns a view of the portion of this set whose elements are strictly
less than toElement.
-
isEmpty()
- Returns true if this set contains no elements.
-
iterator()
- Returns an iterator over the elements in this set.
-
last()
- Returns the last (highest) element currently in this sorted set.
-
remove(Object)
- Removes the given element from this set if it is present.
-
size()
- Returns the number of elements in this set (its cardinality).
-
subSet(Object, Object)
- Returns a view of the portion of this set whose elements range from
fromElement, inclusive, to toElement, exclusive.
-
tailSet(Object)
- Returns a view of the portion of this set whose elements are
greater than or equal to fromElement.
TreeSet
public TreeSet()
- Constructs a new, empty set, sorted according to the elements' natural
order. All elements inserted into the set must implement the
Comparable interface. Furthermore, all such elements must be
mutually comparable: e1.compareTo(e2) must not throw a
ClassCastException for any elements e1 and
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
add(Object) call will throw a ClassCastException.
- See Also:
- Comparable
TreeSet
public TreeSet(Comparator c)
- Constructs a new, empty set, sorted according to the given comparator.
All elements inserted into the set must be mutually comparable
by the given comparator: comparator.compare(e1, e2) must not
throw a ClassCastException for any elements e1 and
e2 in the set. If the user attempts to add an element to the
set that violates this constraint, the add(Object) call will
throw a ClassCastException.
TreeSet
public TreeSet(Collection c)
- Constructs a new set containing the elements in the specified
collection, sorted according to the elements' natural order.
All keys inserted into the set must implement the Comparable
interface. Furthermore, all such keys must be mutually
comparable: k1.compareTo(k2) must not throw a
ClassCastException for any elements k1 and
k2 in the set.
- Parameters:
- c - The elements that will comprise the new set.
TreeSet
public TreeSet(SortedSet s)
- Constructs a new set containing the same elements as the given sorted
set, sorted according to the same ordering.
- Parameters:
- s - sorted set whose elements will comprise the new set.
iterator
public Iterator iterator()
- Returns an iterator over the elements in this set. The elements
are returned in ascending order.
- Returns:
- an iterator over the elements in this set.
- Overrides:
- iterator in class AbstractCollection
size
public int size()
- Returns the number of elements in this set (its cardinality).
- Returns:
- the number of elements in this set (its cardinality).
- Overrides:
- size in class AbstractCollection
isEmpty
public boolean isEmpty()
- Returns true if this set contains no elements.
- Returns:
- true if this set contains no elements.
- Overrides:
- isEmpty in class AbstractCollection
contains
public boolean contains(Object o)
- Returns true if this set contains the specified element.
- Parameters:
- o - the object to be checked for containment in this set.
- Returns:
- true if this set contains the specified element.
- Overrides:
- contains in class AbstractCollection
add
public boolean add(Object o)
- Adds the specified element to this set if it is not already present.
- Parameters:
- o - element to be added to this set.
- Returns:
- true if the set did not already contain the specified
element.
- Overrides:
- add in class AbstractCollection
remove
public boolean remove(Object o)
- Removes the given element from this set if it is present.
- Parameters:
- o - object to be removed from this set, if present.
- Returns:
- true if the set contained the specified element.
- Overrides:
- remove in class AbstractCollection
clear
public void clear()
- Removes all of the elements from this set.
- Overrides:
- clear in class AbstractCollection
addAll
public boolean addAll(Collection c)
- Adds all of the elements in the specified collection to this set.
- Parameters:
- c - elements to be added
- Returns:
- true if this set changed as a result of the call.
- Overrides:
- addAll in class AbstractCollection
subSet
public SortedSet subSet(Object fromElement,
Object toElement)
- Returns a view of the portion of this set whose elements range from
fromElement, inclusive, to toElement, exclusive. (If
fromElement and toElement are equal, the returned
sorted set is empty.) The returned sorted set is backed by this set,
so changes in the returned sorted set are reflected in this set, and
vice-versa. The returned sorted set supports all optional Set
operations.
The sorted set returned by this method will throw an
IllegalArgumentException if the user attempts to insert an
element outside the specified range.
Note: this method always returns a half-open range (which
includes its low endpoint but not its high endpoint). If you need a
closed range (which includes both endpoints), and the element
type allows for calculation of the successor a given value, merely
request the subrange from lowEndpoint to
successor(highEndpoint). For example, suppose that s
is a sorted set of strings. The following idiom obtains a view
containing all of the strings in s from low to
high, inclusive:
SortedSet sub = s.subSet(low, high+"\0");
A similar technique can be used to generate an open range (which
contains neither endpoint). The following idiom obtains a view
containing all of the strings in s from low to
high, exclusive:
SortedSet sub = s.subSet(low+"\0", high);
- Parameters:
- fromElement - low endpoint (inclusive) of the subSet.
- toElement - high endpoint (exclusive) of the subSet.
- Returns:
- a view of the portion of this set whose elements range from
fromElement, inclusive, to toElement,
exclusive.
headSet
public SortedSet headSet(Object toElement)
- Returns a view of the portion of this set whose elements are strictly
less than toElement. The returned sorted set is backed by
this set, so changes in the returned sorted set are reflected in this
set, and vice-versa. The returned sorted set supports all optional set
operations.
The sorted set returned by this method will throw an
IllegalArgumentException if the user attempts to insert an
element greater than or equal to toElement.
Note: this method always returns a view that does not contain its
(high) endpoint. If you need a view that does contain this endpoint,
and the element type allows for calculation of the successor a given
value, merely request a headSet bounded by
successor(highEndpoint). For example, suppose that s
is a sorted set of strings. The following idiom obtains a view
containing all of the strings in s that are less than or equal
to high:
SortedSet head = s.headSet(high+"\0");
- Parameters:
- toElement - high endpoint (exclusive) of the headSet.
- Returns:
- a view of the portion of this set whose elements are strictly
less than toElement.
tailSet
public SortedSet tailSet(Object fromElement)
- Returns a view of the portion of this set whose elements are
greater than or equal to fromElement. The returned sorted set
is backed by this set, so changes in the returned sorted set are
reflected in this set, and vice-versa. The returned sorted set
supports all optional set operations.
The sorted set returned by this method will throw an
IllegalArgumentException if the user attempts to insert an
element less than fromElement.
Note: this method always returns a view that contains its (low)
endpoint. If you need a view that does not contain this endpoint, and
the element type allows for calculation of the successor a given value,
merely request a tailSet bounded by successor(lowEndpoint).
For example, suppose that s is a sorted set of strings. The
following idiom obtains a view containing all of the strings in
s that are strictly greater than low:
SortedSet tail = s.tailSet(low+"\0");
- Parameters:
- fromElement - low endpoint (inclusive) of the tailSet.
- Returns:
- a view of the portion of this set whose elements are
greater than or equal to fromElement.
comparator
public Comparator comparator()
- Returns the comparator used to order this sorted set, or null
if this tree map uses its keys natural ordering.
- Returns:
- the comparator used to order this sorted set, or null
if this tree map uses its keys natural ordering.
first
public Object first()
- Returns the first (lowest) element currently in this sorted set.
- Returns:
- the first (lowest) element currently in this sorted set.
last
public Object last()
- Returns the last (highest) element currently in this sorted set.
- Returns:
- the last (highest) element currently in this sorted set.
clone
public Object clone()
- Returns a shallow copy of this TreeSet instance. (The elements
themselves are not cloned.)
- Returns:
- a shallow copy of this set.
- Overrides:
- clone in class Object
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