*
* This implementation is not synchronized. If you need to share this between
* multiple threads, do something like:
* SortedMap m
* = Collections.synchronizedSortedMap(new TreeMap(...));
*
* The iterators are fail-fast, meaning that any structural
* modification, except for
*
* Note that the iterators for all three views, from keySet(), entrySet(),
* and values(), traverse the TreeMap in sorted sequence.
*
* @return a set view of the entries
* @see #keySet()
* @see #values()
* @see Map.Entry
*/
public Set entrySet()
{
if (entries == null)
// Create an AbstractSet with custom implementations of those methods
// that can be overriden easily and efficiently.
entries = new AbstractSet()
{
public int size()
{
return size;
}
public Iterator iterator()
{
return new TreeIterator(ENTRIES);
}
public void clear()
{
TreeMap.this.clear();
}
public boolean contains(Object o)
{
if (! (o instanceof Map.Entry))
return false;
Map.Entry me = (Map.Entry) o;
Node n = getNode(me.getKey());
return n != nil && AbstractSet.equals(me.getValue(), n.value);
}
public boolean remove(Object o)
{
if (! (o instanceof Map.Entry))
return false;
Map.Entry me = (Map.Entry) o;
Node n = getNode(me.getKey());
if (n != nil && AbstractSet.equals(me.getValue(), n.value))
{
removeNode(n);
return true;
}
return false;
}
};
return entries;
}
/**
* Returns the first (lowest) key in the map.
*
* @return the first key
* @throws NoSuchElementException if the map is empty
*/
public Object firstKey()
{
if (root == nil)
throw new NoSuchElementException();
return firstNode().key;
}
/**
* Return the value in this TreeMap associated with the supplied key,
* or remove() called on the iterator
* itself, cause the iterator to throw a
* ConcurrentModificationException rather than exhibit
* non-deterministic behavior.
*
* @author Jon Zeppieri
* @author Bryce McKinlay
* @author Eric Blake null if the key maps to nothing. NOTE: Since the value
* could also be null, you must use containsKey to see if this key
* actually maps to something.
*
* @param key the key for which to fetch an associated value
* @return what the key maps to, if present
* @throws ClassCastException if key is not comparable to elements in the map
* @throws NullPointerException if key is null but the comparator does not
* tolerate nulls
* @see #put(Object, Object)
* @see #containsKey(Object)
*/
public Object get(Object key)
{
// Exploit fact that nil.value == null.
return getNode(key).value;
}
/**
* Returns a view of this Map including all entries with keys less than
* toKey. The returned map is backed by the original, so changes
* in one appear in the other. The submap will throw an
* {@link IllegalArgumentException} for any attempt to access or add an
* element beyond the specified cutoff. The returned map does not include
* the endpoint; if you want inclusion, pass the successor element.
*
* @param toKey the (exclusive) cutoff point
* @return a view of the map less than the cutoff
* @throws ClassCastException if toKey is not compatible with
* the comparator (or is not Comparable, for natural ordering)
* @throws NullPointerException if toKey is null, but the comparator does not
* tolerate null elements
*/
public SortedMap headMap(Object toKey)
{
return new SubMap(nil, toKey);
}
/**
* Returns a "set view" of this TreeMap's keys. The set is backed by the
* TreeMap, so changes in one show up in the other. The set supports
* element removal, but not element addition.
*
* @return a set view of the keys
* @see #values()
* @see #entrySet()
*/
public Set keySet()
{
if (keys == null)
// Create an AbstractSet with custom implementations of those methods
// that can be overriden easily and efficiently.
keys = new AbstractSet()
{
public int size()
{
return size;
}
public Iterator iterator()
{
return new TreeIterator(KEYS);
}
public void clear()
{
TreeMap.this.clear();
}
public boolean contains(Object o)
{
return containsKey(o);
}
public boolean remove(Object key)
{
Node n = getNode(key);
if (n == nil)
return false;
removeNode(n);
return true;
}
};
return keys;
}
/**
* Returns the last (highest) key in the map.
*
* @return the last key
* @throws NoSuchElementException if the map is empty
*/
public Object lastKey()
{
if (root == nil)
throw new NoSuchElementException("empty");
return lastNode().key;
}
/**
* Puts the supplied value into the Map, mapped by the supplied key.
* The value may be retrieved by any object which equals()
* this key. NOTE: Since the prior value could also be null, you must
* first use containsKey if you want to see if you are replacing the
* key's mapping.
*
* @param key the key used to locate the value
* @param value the value to be stored in the HashMap
* @return the prior mapping of the key, or null if there was none
* @throws ClassCastException if key is not comparable to current map keys
* @throws NullPointerException if key is null, but the comparator does
* not tolerate nulls
* @see #get(Object)
* @see Object#equals(Object)
*/
public Object put(Object key, Object value)
{
Node current = root;
Node parent = nil;
int comparison = 0;
// Find new node's parent.
while (current != nil)
{
parent = current;
comparison = compare(key, current.key);
if (comparison > 0)
current = current.right;
else if (comparison < 0)
current = current.left;
else // Key already in tree.
return current.setValue(value);
}
// Set up new node.
Node n = new Node(key, value, RED);
n.parent = parent;
// Insert node in tree.
modCount++;
size++;
if (parent == nil)
{
// Special case inserting into an empty tree.
root = n;
return null;
}
if (comparison > 0)
parent.right = n;
else
parent.left = n;
// Rebalance after insert.
insertFixup(n);
return null;
}
/**
* Copies all elements of the given map into this hashtable. If this table
* already has a mapping for a key, the new mapping replaces the current
* one.
*
* @param m the map to be hashed into this
* @throws ClassCastException if a key in m is not comparable with keys
* in the map
* @throws NullPointerException if a key in m is null, and the comparator
* does not tolerate nulls
*/
public void putAll(Map m)
{
Iterator itr = m.entrySet().iterator();
int pos = m.size();
while (--pos >= 0)
{
Map.Entry e = (Map.Entry) itr.next();
put(e.getKey(), e.getValue());
}
}
/**
* Removes from the TreeMap and returns the value which is mapped by the
* supplied key. If the key maps to nothing, then the TreeMap remains
* unchanged, and null is returned. NOTE: Since the value
* could also be null, you must use containsKey to see if you are
* actually removing a mapping.
*
* @param key the key used to locate the value to remove
* @return whatever the key mapped to, if present
* @throws ClassCastException if key is not comparable to current map keys
* @throws NullPointerException if key is null, but the comparator does
* not tolerate nulls
*/
public Object remove(Object key)
{
Node n = getNode(key);
if (n == nil)
return null;
// Note: removeNode can alter the contents of n, so save value now.
Object result = n.value;
removeNode(n);
return result;
}
/**
* Returns the number of key-value mappings currently in this Map.
*
* @return the size
*/
public int size()
{
return size;
}
/**
* Returns a view of this Map including all entries with keys greater or
* equal to fromKey and less than toKey (a
* half-open interval). The returned map is backed by the original, so
* changes in one appear in the other. The submap will throw an
* {@link IllegalArgumentException} for any attempt to access or add an
* element beyond the specified cutoffs. The returned map includes the low
* endpoint but not the high; if you want to reverse this behavior on
* either end, pass in the successor element.
*
* @param fromKey the (inclusive) low cutoff point
* @param toKey the (exclusive) high cutoff point
* @return a view of the map between the cutoffs
* @throws ClassCastException if either cutoff is not compatible with
* the comparator (or is not Comparable, for natural ordering)
* @throws NullPointerException if fromKey or toKey is null, but the
* comparator does not tolerate null elements
* @throws IllegalArgumentException if fromKey is greater than toKey
*/
public SortedMap subMap(Object fromKey, Object toKey)
{
return new SubMap(fromKey, toKey);
}
/**
* Returns a view of this Map including all entries with keys greater or
* equal to fromKey. The returned map is backed by the
* original, so changes in one appear in the other. The submap will throw an
* {@link IllegalArgumentException} for any attempt to access or add an
* element beyond the specified cutoff. The returned map includes the
* endpoint; if you want to exclude it, pass in the successor element.
*
* @param fromKey the (inclusive) low cutoff point
* @return a view of the map above the cutoff
* @throws ClassCastException if fromKey is not compatible with
* the comparator (or is not Comparable, for natural ordering)
* @throws NullPointerException if fromKey is null, but the comparator
* does not tolerate null elements
*/
public SortedMap tailMap(Object fromKey)
{
return new SubMap(fromKey, nil);
}
/**
* Returns a "collection view" (or "bag view") of this TreeMap's values.
* The collection is backed by the TreeMap, so changes in one show up
* in the other. The collection supports element removal, but not element
* addition.
*
* @return a bag view of the values
* @see #keySet()
* @see #entrySet()
*/
public Collection values()
{
if (values == null)
// We don't bother overriding many of the optional methods, as doing so
// wouldn't provide any significant performance advantage.
values = new AbstractCollection()
{
public int size()
{
return size;
}
public Iterator iterator()
{
return new TreeIterator(VALUES);
}
public void clear()
{
TreeMap.this.clear();
}
};
return values;
}
/**
* Compares two elements by the set comparator, or by natural ordering.
* Package visible for use by nested classes.
*
* @param o1 the first object
* @param o2 the second object
* @throws ClassCastException if o1 and o2 are not mutually comparable,
* or are not Comparable with natural ordering
* @throws NullPointerException if o1 or o2 is null with natural ordering
*/
final int compare(Object o1, Object o2)
{
return (comparator == null
? ((Comparable) o1).compareTo(o2)
: comparator.compare(o1, o2));
}
/**
* Maintain red-black balance after deleting a node.
*
* @param node the child of the node just deleted, possibly nil
* @param parent the parent of the node just deleted, never nil
*/
private void deleteFixup(Node node, Node parent)
{
// if (parent == nil)
// throw new InternalError();
// If a black node has been removed, we need to rebalance to avoid
// violating the "same number of black nodes on any path" rule. If
// node is red, we can simply recolor it black and all is well.
while (node != root && node.color == BLACK)
{
if (node == parent.left)
{
// Rebalance left side.
Node sibling = parent.right;
// if (sibling == nil)
// throw new InternalError();
if (sibling.color == RED)
{
// Case 1: Sibling is red.
// Recolor sibling and parent, and rotate parent left.
sibling.color = BLACK;
parent.color = RED;
rotateLeft(parent);
sibling = parent.right;
}
if (sibling.left.color == BLACK && sibling.right.color == BLACK)
{
// Case 2: Sibling has no red children.
// Recolor sibling, and move to parent.
sibling.color = RED;
node = parent;
parent = parent.parent;
}
else
{
if (sibling.right.color == BLACK)
{
// Case 3: Sibling has red left child.
// Recolor sibling and left child, rotate sibling right.
sibling.left.color = BLACK;
sibling.color = RED;
rotateRight(sibling);
sibling = parent.right;
}
// Case 4: Sibling has red right child. Recolor sibling,
// right child, and parent, and rotate parent left.
sibling.color = parent.color;
parent.color = BLACK;
sibling.right.color = BLACK;
rotateLeft(parent);
node = root; // Finished.
}
}
else
{
// Symmetric "mirror" of left-side case.
Node sibling = parent.left;
// if (sibling == nil)
// throw new InternalError();
if (sibling.color == RED)
{
// Case 1: Sibling is red.
// Recolor sibling and parent, and rotate parent right.
sibling.color = BLACK;
parent.color = RED;
rotateRight(parent);
sibling = parent.left;
}
if (sibling.right.color == BLACK && sibling.left.color == BLACK)
{
// Case 2: Sibling has no red children.
// Recolor sibling, and move to parent.
sibling.color = RED;
node = parent;
parent = parent.parent;
}
else
{
if (sibling.left.color == BLACK)
{
// Case 3: Sibling has red right child.
// Recolor sibling and right child, rotate sibling left.
sibling.right.color = BLACK;
sibling.color = RED;
rotateLeft(sibling);
sibling = parent.left;
}
// Case 4: Sibling has red left child. Recolor sibling,
// left child, and parent, and rotate parent right.
sibling.color = parent.color;
parent.color = BLACK;
sibling.left.color = BLACK;
rotateRight(parent);
node = root; // Finished.
}
}
}
node.color = BLACK;
}
/**
* Construct a perfectly balanced tree consisting of n "blank" nodes. This
* permits a tree to be generated from pre-sorted input in linear time.
*
* @param count the number of blank nodes, non-negative
*/
private void fabricateTree(final int count)
{
if (count == 0)
return;
// We color every row of nodes black, except for the overflow nodes.
// I believe that this is the optimal arrangement. We construct the tree
// in place by temporarily linking each node to the next node in the row,
// then updating those links to the children when working on the next row.
// Make the root node.
root = new Node(null, null, BLACK);
size = count;
Node row = root;
int rowsize;
// Fill each row that is completely full of nodes.
for (rowsize = 2; rowsize + rowsize <= count; rowsize <<= 1)
{
Node parent = row;
Node last = null;
for (int i = 0; i < rowsize; i += 2)
{
Node left = new Node(null, null, BLACK);
Node right = new Node(null, null, BLACK);
left.parent = parent;
left.right = right;
right.parent = parent;
parent.left = left;
Node next = parent.right;
parent.right = right;
parent = next;
if (last != null)
last.right = left;
last = right;
}
row = row.left;
}
// Now do the partial final row in red.
int overflow = count - rowsize;
Node parent = row;
int i;
for (i = 0; i < overflow; i += 2)
{
Node left = new Node(null, null, RED);
Node right = new Node(null, null, RED);
left.parent = parent;
right.parent = parent;
parent.left = left;
Node next = parent.right;
parent.right = right;
parent = next;
}
// Add a lone left node if necessary.
if (i - overflow == 0)
{
Node left = new Node(null, null, RED);
left.parent = parent;
parent.left = left;
parent = parent.right;
left.parent.right = nil;
}
// Unlink the remaining nodes of the previous row.
while (parent != nil)
{
Node next = parent.right;
parent.right = nil;
parent = next;
}
}
/**
* Returns the first sorted node in the map, or nil if empty. Package
* visible for use by nested classes.
*
* @return the first node
*/
final Node firstNode()
{
// Exploit fact that nil.left == nil.
Node node = root;
while (node.left != nil)
node = node.left;
return node;
}
/**
* Return the TreeMap.Node associated with key, or the nil node if no such
* node exists in the tree. Package visible for use by nested classes.
*
* @param key the key to search for
* @return the node where the key is found, or nil
*/
final Node getNode(Object key)
{
Node current = root;
while (current != nil)
{
int comparison = compare(key, current.key);
if (comparison > 0)
current = current.right;
else if (comparison < 0)
current = current.left;
else
return current;
}
return current;
}
/**
* Find the "highest" node which is < key. If key is nil, return last
* node. Package visible for use by nested classes.
*
* @param key the upper bound, exclusive
* @return the previous node
*/
final Node highestLessThan(Object key)
{
if (key == nil)
return lastNode();
Node last = nil;
Node current = root;
int comparison = 0;
while (current != nil)
{
last = current;
comparison = compare(key, current.key);
if (comparison > 0)
current = current.right;
else if (comparison < 0)
current = current.left;
else // Exact match.
return predecessor(last);
}
return comparison <= 0 ? predecessor(last) : last;
}
/**
* Maintain red-black balance after inserting a new node.
*
* @param n the newly inserted node
*/
private void insertFixup(Node n)
{
// Only need to rebalance when parent is a RED node, and while at least
// 2 levels deep into the tree (ie: node has a grandparent). Remember
// that nil.color == BLACK.
while (n.parent.color == RED && n.parent.parent != nil)
{
if (n.parent == n.parent.parent.left)
{
Node uncle = n.parent.parent.right;
// Uncle may be nil, in which case it is BLACK.
if (uncle.color == RED)
{
// Case 1. Uncle is RED: Change colors of parent, uncle,
// and grandparent, and move n to grandparent.
n.parent.color = BLACK;
uncle.color = BLACK;
uncle.parent.color = RED;
n = uncle.parent;
}
else
{
if (n == n.parent.right)
{
// Case 2. Uncle is BLACK and x is right child.
// Move n to parent, and rotate n left.
n = n.parent;
rotateLeft(n);
}
// Case 3. Uncle is BLACK and x is left child.
// Recolor parent, grandparent, and rotate grandparent right.
n.parent.color = BLACK;
n.parent.parent.color = RED;
rotateRight(n.parent.parent);
}
}
else
{
// Mirror image of above code.
Node uncle = n.parent.parent.left;
// Uncle may be nil, in which case it is BLACK.
if (uncle.color == RED)
{
// Case 1. Uncle is RED: Change colors of parent, uncle,
// and grandparent, and move n to grandparent.
n.parent.color = BLACK;
uncle.color = BLACK;
uncle.parent.color = RED;
n = uncle.parent;
}
else
{
if (n == n.parent.left)
{
// Case 2. Uncle is BLACK and x is left child.
// Move n to parent, and rotate n right.
n = n.parent;
rotateRight(n);
}
// Case 3. Uncle is BLACK and x is right child.
// Recolor parent, grandparent, and rotate grandparent left.
n.parent.color = BLACK;
n.parent.parent.color = RED;
rotateLeft(n.parent.parent);
}
}
}
root.color = BLACK;
}
/**
* Returns the last sorted node in the map, or nil if empty.
*
* @return the last node
*/
private Node lastNode()
{
// Exploit fact that nil.right == nil.
Node node = root;
while (node.right != nil)
node = node.right;
return node;
}
/**
* Find the "lowest" node which is >= key. If key is nil, return either
* nil or the first node, depending on the parameter first.
* Package visible for use by nested classes.
*
* @param key the lower bound, inclusive
* @param first true to return the first element instead of nil for nil key
* @return the next node
*/
final Node lowestGreaterThan(Object key, boolean first)
{
if (key == nil)
return first ? firstNode() : nil;
Node last = nil;
Node current = root;
int comparison = 0;
while (current != nil)
{
last = current;
comparison = compare(key, current.key);
if (comparison > 0)
current = current.right;
else if (comparison < 0)
current = current.left;
else
return current;
}
return comparison > 0 ? successor(last) : last;
}
/**
* Return the node preceding the given one, or nil if there isn't one.
*
* @param node the current node, not nil
* @return the prior node in sorted order
*/
private Node predecessor(Node node)
{
if (node.left != nil)
{
node = node.left;
while (node.right != nil)
node = node.right;
return node;
}
Node parent = node.parent;
// Exploit fact that nil.left == nil and node is non-nil.
while (node == parent.left)
{
node = parent;
parent = node.parent;
}
return parent;
}
/**
* Construct a tree from sorted keys in linear time. Package visible for
* use by TreeSet.
*
* @param s the stream to read from
* @param count the number of keys to read
* @param readValue true to read values, false to insert "" as the value
* @throws ClassNotFoundException if the underlying stream fails
* @throws IOException if the underlying stream fails
* @see #readObject(ObjectInputStream)
* @see TreeSet#readObject(ObjectInputStream)
*/
final void putFromObjStream(ObjectInputStream s, int count,
boolean readValues)
throws IOException, ClassNotFoundException
{
fabricateTree(count);
Node node = firstNode();
while (--count >= 0)
{
node.key = s.readObject();
node.value = readValues ? s.readObject() : "";
node = successor(node);
}
}
/**
* Construct a tree from sorted keys in linear time, with values of "".
* Package visible for use by TreeSet.
*
* @param keys the iterator over the sorted keys
* @param count the number of nodes to insert
* @see TreeSet#TreeSet(SortedSet)
*/
final void putKeysLinear(Iterator keys, int count)
{
fabricateTree(count);
Node node = firstNode();
while (--count >= 0)
{
node.key = keys.next();
node.value = "";
node = successor(node);
}
}
/**
* Deserializes this object from the given stream.
*
* @param s the stream to read from
* @throws ClassNotFoundException if the underlying stream fails
* @throws IOException if the underlying stream fails
* @serialData the size (int), followed by key (Object) and value
* (Object) pairs in sorted order
*/
private void readObject(ObjectInputStream s)
throws IOException, ClassNotFoundException
{
s.defaultReadObject();
int size = s.readInt();
putFromObjStream(s, size, true);
}
/**
* Remove node from tree. This will increment modCount and decrement size.
* Node must exist in the tree. Package visible for use by nested classes.
*
* @param node the node to remove
*/
final void removeNode(Node node)
{
Node splice;
Node child;
modCount++;
size--;
// Find splice, the node at the position to actually remove from the tree.
if (node.left == nil)
{
// Node to be deleted has 0 or 1 children.
splice = node;
child = node.right;
}
else if (node.right == nil)
{
// Node to be deleted has 1 child.
splice = node;
child = node.left;
}
else
{
// Node has 2 children. Splice is node's predecessor, and we swap
// its contents into node.
splice = node.left;
while (splice.right != nil)
splice = splice.right;
child = splice.left;
node.key = splice.key;
node.value = splice.value;
}
// Unlink splice from the tree.
Node parent = splice.parent;
if (child != nil)
child.parent = parent;
if (parent == nil)
{
// Special case for 0 or 1 node remaining.
root = child;
return;
}
if (splice == parent.left)
parent.left = child;
else
parent.right = child;
if (splice.color == BLACK)
deleteFixup(child, parent);
}
/**
* Rotate node n to the left.
*
* @param node the node to rotate
*/
private void rotateLeft(Node node)
{
Node child = node.right;
// if (node == nil || child == nil)
// throw new InternalError();
// Establish node.right link.
node.right = child.left;
if (child.left != nil)
child.left.parent = node;
// Establish child->parent link.
child.parent = node.parent;
if (node.parent != nil)
{
if (node == node.parent.left)
node.parent.left = child;
else
node.parent.right = child;
}
else
root = child;
// Link n and child.
child.left = node;
node.parent = child;
}
/**
* Rotate node n to the right.
*
* @param node the node to rotate
*/
private void rotateRight(Node node)
{
Node child = node.left;
// if (node == nil || child == nil)
// throw new InternalError();
// Establish node.left link.
node.left = child.right;
if (child.right != nil)
child.right.parent = node;
// Establish child->parent link.
child.parent = node.parent;
if (node.parent != nil)
{
if (node == node.parent.right)
node.parent.right = child;
else
node.parent.left = child;
}
else
root = child;
// Link n and child.
child.right = node;
node.parent = child;
}
/**
* Return the node following the given one, or nil if there isn't one.
* Package visible for use by nested classes.
*
* @param node the current node, not nil
* @return the next node in sorted order
*/
final Node successor(Node node)
{
if (node.right != nil)
{
node = node.right;
while (node.left != nil)
node = node.left;
return node;
}
Node parent = node.parent;
// Exploit fact that nil.right == nil and node is non-nil.
while (node == parent.right)
{
node = parent;
parent = parent.parent;
}
return parent;
}
/**
* Serializes this object to the given stream.
*
* @param s the stream to write to
* @throws IOException if the underlying stream fails
* @serialData the size (int), followed by key (Object) and value
* (Object) pairs in sorted order
*/
private void writeObject(ObjectOutputStream s) throws IOException
{
s.defaultWriteObject();
Node node = firstNode();
s.writeInt(size);
while (node != nil)
{
s.writeObject(node.key);
s.writeObject(node.value);
node = successor(node);
}
}
/**
* Iterate over HashMap's entries. This implementation is parameterized
* to give a sequential view of keys, values, or entries.
*
* @author Eric Blake next() method.
* @throws ConcurrentModificationException if the TreeMap was modified
* @throws IllegalStateException if called when there is no last element
*/
public void remove()
{
if (last == null)
throw new IllegalStateException();
if (knownMod != modCount)
throw new ConcurrentModificationException();
removeNode(last);
last = null;
knownMod++;
}
} // class TreeIterator
/**
* Implementation of {@link #subMap(Object, Object)} and other map
* ranges. This class provides a view of a portion of the original backing
* map, and throws {@link IllegalArgumentException} for attempts to
* access beyond that range.
*
* @author Eric Blake