讀TreeMap源碼

//一個基於二叉紅黑樹實現的map
//關於紅黑樹http://blog.csdn.net/chenssy/article/details/26668941這篇博客寫的非常好
//另外TreeSet的是用TreeMap實現的。(組合設計模式,將所有的實現委託給TreeMap實現)
//先看構造函數
 public TreeMap() {
        comparator = null;
    }


public TreeMap(Comparator<? super K> comparator) {
        this.comparator = comparator;
    }


 public TreeMap(Map<? extends K, ? extends V> m) {
        comparator = null;
        putAll(m);
    }

//新增
 public V put(K key, V value) {
        Entry<K,V> t = root;
	//如果root是null,則直接放入root。
        if (t == null) {
	    //檢查是否實現了Comparable接口,以及釋放傳入的是null
            compare(key, key); // type (and possibly null) check

            root = new Entry<>(key, value, null);
            size = 1;
            modCount++;
            return null;
        }

        int cmp;
        Entry<K,V> parent;
        // split comparator and comparable paths
        Comparator<? super K> cpr = comparator;
	//如果傳入了comparator
        if (cpr != null) {
            do {
	    //無限循環設置位置
                parent = t;
                cmp = cpr.compare(key, t.key);
		//如果比父節點小則放在左邊
                if (cmp < 0)
                    t = t.left;
		 //大則放在右邊
                else if (cmp > 0)
                    t = t.right;
		    //相當則新值代替舊值
                else
                    return t.setValue(value);
            } while (t != null);
        }
	//如果Comparable是null
        else {
            if (key == null)
                throw new NullPointerException();
            Comparable<? super K> k = (Comparable<? super K>) key;
            do {
	       //無限循環設置位置
                parent = t;
                cmp = k.compareTo(t.key);
                if (cmp < 0)
                    t = t.left;
                else if (cmp > 0)
                    t = t.right;
                else
                    return t.setValue(value);
            } while (t != null);
        }
        Entry<K,V> e = new Entry<>(key, value, parent);
        if (cmp < 0)
            parent.left = e;
        else
            parent.right = e;
	 //平衡整棵樹
        fixAfterInsertion(e);
        size++;
        modCount++;
        return null;
    }

 private void fixAfterInsertion(Entry<K,V> x) {
        x.color = RED;

        while (x != null && x != root && x.parent.color == RED) {
            if (parentOf(x) == leftOf(parentOf(parentOf(x)))) {
                Entry<K,V> y = rightOf(parentOf(parentOf(x)));
                if (colorOf(y) == RED) {
                    setColor(parentOf(x), BLACK);
                    setColor(y, BLACK);
                    setColor(parentOf(parentOf(x)), RED);
                    x = parentOf(parentOf(x));
                } else {
                    if (x == rightOf(parentOf(x))) {
                        x = parentOf(x);
                        rotateLeft(x);
                    }
                    setColor(parentOf(x), BLACK);
                    setColor(parentOf(parentOf(x)), RED);
                    rotateRight(parentOf(parentOf(x)));
                }
            } else {
                Entry<K,V> y = leftOf(parentOf(parentOf(x)));
                if (colorOf(y) == RED) {
                    setColor(parentOf(x), BLACK);
                    setColor(y, BLACK);
                    setColor(parentOf(parentOf(x)), RED);
                    x = parentOf(parentOf(x));
                } else {
                    if (x == leftOf(parentOf(x))) {
                        x = parentOf(x);
                        rotateRight(x);
                    }
                    setColor(parentOf(x), BLACK);
                    setColor(parentOf(parentOf(x)), RED);
                    rotateLeft(parentOf(parentOf(x)));
                }
            }
        }
        root.color = BLACK;
    }

   final int compare(Object k1, Object k2) {
        return comparator==null ? ((Comparable<? super K>)k1).compareTo((K)k2)
            : comparator.compare((K)k1, (K)k2);
    }


//新增map
public void putAll(Map<? extends K, ? extends V> map) {
        int mapSize = map.size();
	//如果當前集合是空的並且map是SortedMap
        if (size==0 && mapSize!=0 && map instanceof SortedMap) {
            Comparator c = ((SortedMap)map).comparator();
	    //如果用的比較器相同
            if (c == comparator || (c != null && c.equals(comparator))) {
                ++modCount;
                try {
                    buildFromSorted(mapSize, map.entrySet().iterator(),
                                    null, null);
                } catch (java.io.IOException cannotHappen) {
                } catch (ClassNotFoundException cannotHappen) {
                }
                return;
            }
        }
	//如果不是put方法
        super.putAll(map);
    }

  private void buildFromSorted(int size, Iterator it,
                                 java.io.ObjectInputStream str,
                                 V defaultVal)
        throws  java.io.IOException, ClassNotFoundException {
        this.size = size;
	//獲取根節點
        root = buildFromSorted(0, 0, size-1, computeRedLevel(size),
                               it, str, defaultVal);
    }

//根據key獲取值
 public V get(Object key) {
        Entry<K,V> p = getEntry(key);
        return (p==null ? null : p.value);
    }


final Entry<K,V> getEntry(Object key) {
        // Offload comparator-based version for sake of performance
        if (comparator != null)
	   //當有比較器
            return getEntryUsingComparator(key);
        if (key == null)
            throw new NullPointerException();
        Comparable<? super K> k = (Comparable<? super K>) key;
        Entry<K,V> p = root;
	//無限循環獲取值
        while (p != null) {
            int cmp = k.compareTo(p.key);
            if (cmp < 0)
                p = p.left;
            else if (cmp > 0)
                p = p.right;
            else
                return p;
        }
        return null;
    }

final Entry<K,V> getEntryUsingComparator(Object key) {
        K k = (K) key;
        Comparator<? super K> cpr = comparator;
        if (cpr != null) {
            Entry<K,V> p = root;
            while (p != null) {
                int cmp = cpr.compare(k, p.key);
                if (cmp < 0)
                    p = p.left;
                else if (cmp > 0)
                    p = p.right;
                else
                    return p;
            }
        }
        return null;
    }

//根據key刪除值
 public V remove(Object key) {
        Entry<K,V> p = getEntry(key);
        if (p == null)
            return null;

        V oldValue = p.value;
        deleteEntry(p);
        return oldValue;
    }


 private void deleteEntry(Entry<K,V> p) {
        modCount++;
        size--;

        // If strictly internal, copy successor's element to p and then make p
        // point to successor.
        if (p.left != null && p.right != null) {
            Entry<K,V> s = successor(p);
            p.key = s.key;
            p.value = s.value;
            p = s;
        } // p has 2 children

        // Start fixup at replacement node, if it exists.
        Entry<K,V> replacement = (p.left != null ? p.left : p.right);

        if (replacement != null) {
            // Link replacement to parent
            replacement.parent = p.parent;
            if (p.parent == null)
                root = replacement;
            else if (p == p.parent.left)
                p.parent.left  = replacement;
            else
                p.parent.right = replacement;

            // Null out links so they are OK to use by fixAfterDeletion.
            p.left = p.right = p.parent = null;

            // Fix replacement
            if (p.color == BLACK)
                fixAfterDeletion(replacement);
        } else if (p.parent == null) { // return if we are the only node.
            root = null;
        } else { //  No children. Use self as phantom replacement and unlink.
            if (p.color == BLACK)
                fixAfterDeletion(p);

            if (p.parent != null) {
                if (p == p.parent.left)
                    p.parent.left = null;
                else if (p == p.parent.right)
                    p.parent.right = null;
                p.parent = null;
            }
        }
    }

//返回map的長度
  public int size() {
        return size;
    }

//是否包含某個鍵
public boolean containsKey(Object key) {
        return getEntry(key) != null;
    }

//是否包含某個值
public boolean containsValue(Object value) {
        for (Entry<K,V> e = getFirstEntry(); e != null; e = successor(e))
            if (valEquals(value, e.value))
                return true;
        return false;
    }

//獲取最左邊的作爲也就是第一個entry
 final Entry<K,V> getFirstEntry() {
        Entry<K,V> p = root;
        if (p != null)
            while (p.left != null)
                p = p.left;
        return p;
    }

//找尋下一個節點
static <K,V> TreeMap.Entry<K,V> successor(Entry<K,V> t) {
        if (t == null)
            return null;
	//如果有右子樹,則尋找右子樹最左邊節點作爲下一個節點
        else if (t.right != null) {
            Entry<K,V> p = t.right;
            while (p.left != null)
                p = p.left;
            return p;
        } else {
	  //沒有就往上找
            Entry<K,V> p = t.parent;
            Entry<K,V> ch = t;
	    //如果是自己,則繼續向上尋找
            while (p != null && ch == p.right) {
                ch = p;
                p = p.parent;
            }
            return p;
        }
    }


static final boolean valEquals(Object o1, Object o2) {
        return (o1==null ? o2==null : o1.equals(o2));
    }

//返回映射中第一個key,即樹最左邊的key
 public K firstKey() {
        return key(getFirstEntry());
    }

 static <K> K key(Entry<K,?> e) {
        if (e==null)
            throw new NoSuchElementException();
        return e.key;
    }


//獲取最後一個 即最右邊的entry
 final Entry<K,V> getLastEntry() {
        Entry<K,V> p = root;
        if (p != null)
            while (p.right != null)
                p = p.right;
        return p;
    }

//獲取最大的鍵即最右邊的鍵
 public K lastKey() {
        return key(getLastEntry());
    }

//清空集合
public void clear() {
        modCount++;
        size = 0;
        root = null;
    }

//獲取最左邊的entry(最低位的entry)
 public Map.Entry<K,V> firstEntry() {
        return exportEntry(getFirstEntry());
    }

//轉成SimpleImmutableEntry。
static <K,V> Map.Entry<K,V> exportEntry(TreeMap.Entry<K,V> e) {
        return (e == null) ? null :
            new AbstractMap.SimpleImmutableEntry<>(e);
    }

//獲取最右邊的entry(最高位的entry)
 public Map.Entry<K,V> lastEntry() {
        return exportEntry(getLastEntry());
    }


//移除最左邊的鍵
 public Map.Entry<K,V> pollFirstEntry() {
        Entry<K,V> p = getFirstEntry();
        Map.Entry<K,V> result = exportEntry(p);
        if (p != null)
            deleteEntry(p);
        return result;
    }

//移除最右邊的鍵
 public Map.Entry<K,V> pollLastEntry() {
        Entry<K,V> p = getLastEntry();
        Map.Entry<K,V> result = exportEntry(p);
        if (p != null)
            deleteEntry(p);
        return result;
    }

//返回小於當前鍵的最大entry
public Map.Entry<K,V> lowerEntry(K key) {
        return exportEntry(getLowerEntry(key));
    }

//返回小於當前鍵的最大entry
   final Entry<K,V> getLowerEntry(K key) {
        Entry<K,V> p = root;
        while (p != null) {
            int cmp = compare(key, p.key);
	    //在根部的右側
            if (cmp > 0) {
                if (p.right != null)
                    p = p.right;
                else
                    return p;
	     //在根據的左側
            } else {
                if (p.left != null) {
                    p = p.left;
                } else {
                    Entry<K,V> parent = p.parent;
                    Entry<K,V> ch = p;
                    while (parent != null && ch == parent.left) {
                        ch = parent;
                        parent = parent.parent;
                    }
                    return parent;
                }
            }
        }
        return null;
    }

//返回小於當前鍵的最大鍵
public K lowerKey(K key) {
        return keyOrNull(getLowerEntry(key));
    }

 static <K,V> K keyOrNull(TreeMap.Entry<K,V> e) {
        return (e == null) ? null : e.key;
    }


//返回小於等於鍵的最大entry
public Map.Entry<K,V> floorEntry(K key) {
        return exportEntry(getFloorEntry(key));
    }

//返回小於等於鍵的最大鍵
public K floorKey(K key) {
        return keyOrNull(getFloorEntry(key));
    }


final Entry<K,V> getFloorEntry(K key) {
        Entry<K,V> p = root;
        while (p != null) {
            int cmp = compare(key, p.key);
            if (cmp > 0) {
                if (p.right != null)
                    p = p.right;
                else
                    return p;
            } else if (cmp < 0) {
                if (p.left != null) {
                    p = p.left;
                } else {
                    Entry<K,V> parent = p.parent;
                    Entry<K,V> ch = p;
                    while (parent != null && ch == parent.left) {
                        ch = parent;
                        parent = parent.parent;
                    }
                    return parent;
                }
            } else
                return p;

        }
        return null;
    }


//返回大於等於給定鍵的最小entry
 public Map.Entry<K,V> ceilingEntry(K key) {
        return exportEntry(getCeilingEntry(key));
    }

//返回大於等於給定鍵的最小key
public K ceilingKey(K key) {
        return keyOrNull(getCeilingEntry(key));
    }

final Entry<K,V> getCeilingEntry(K key) {
        Entry<K,V> p = root;
        while (p != null) {
            int cmp = compare(key, p.key);
            if (cmp < 0) {
                if (p.left != null)
                    p = p.left;
                else
                    return p;
            } else if (cmp > 0) {
                if (p.right != null) {
                    p = p.right;
                } else {
                    Entry<K,V> parent = p.parent;
                    Entry<K,V> ch = p;
                    while (parent != null && ch == parent.right) {
                        ch = parent;
                        parent = parent.parent;
                    }
                    return parent;
                }
            } else
                return p;
        }
        return null;
    }

//返回大於key的最小entry
 public Map.Entry<K,V> higherEntry(K key) {
        return exportEntry(getHigherEntry(key));
    }

//返回大於key的最小key
 public K higherKey(K key) {
        return keyOrNull(getHigherEntry(key));
    }


 final Entry<K,V> getHigherEntry(K key) {
        Entry<K,V> p = root;
        while (p != null) {
            int cmp = compare(key, p.key);
            if (cmp < 0) {
                if (p.left != null)
                    p = p.left;
                else
                    return p;
            } else {
                if (p.right != null) {
                    p = p.right;
                } else {
                    Entry<K,V> parent = p.parent;
                    Entry<K,V> ch = p;
                    while (parent != null && ch == parent.right) {
                        ch = parent;
                        parent = parent.parent;
                    }
                    return parent;
                }
            }
        }
        return null;
    }


//返回key的set集合
 public Set<K> keySet() {
        return navigableKeySet();
    }

 public NavigableSet<K> navigableKeySet() {
        KeySet<K> nks = navigableKeySet;
        return (nks != null) ? nks : (navigableKeySet = new KeySet(this));
    }


  static final class KeySet<E> extends AbstractSet<E> implements NavigableSet<E> {
        private final NavigableMap<E, Object> m;
        KeySet(NavigableMap<E,Object> map) { m = map; }

        public Iterator<E> iterator() {
            if (m instanceof TreeMap)
                return ((TreeMap<E,Object>)m).keyIterator();
            else
                return (Iterator<E>)(((TreeMap.NavigableSubMap)m).keyIterator());
        }

        public Iterator<E> descendingIterator() {
            if (m instanceof TreeMap)
                return ((TreeMap<E,Object>)m).descendingKeyIterator();
            else
                return (Iterator<E>)(((TreeMap.NavigableSubMap)m).descendingKeyIterator());
        }

        public int size() { return m.size(); }
        public boolean isEmpty() { return m.isEmpty(); }
        public boolean contains(Object o) { return m.containsKey(o); }
        public void clear() { m.clear(); }
        public E lower(E e) { return m.lowerKey(e); }
        public E floor(E e) { return m.floorKey(e); }
        public E ceiling(E e) { return m.ceilingKey(e); }
        public E higher(E e) { return m.higherKey(e); }
        public E first() { return m.firstKey(); }
        public E last() { return m.lastKey(); }
        public Comparator<? super E> comparator() { return m.comparator(); }
        public E pollFirst() {
            Map.Entry<E,Object> e = m.pollFirstEntry();
            return (e == null) ? null : e.getKey();
        }
        public E pollLast() {
            Map.Entry<E,Object> e = m.pollLastEntry();
            return (e == null) ? null : e.getKey();
        }
        public boolean remove(Object o) {
            int oldSize = size();
            m.remove(o);
            return size() != oldSize;
        }
        public NavigableSet<E> subSet(E fromElement, boolean fromInclusive,
                                      E toElement,   boolean toInclusive) {
            return new KeySet<>(m.subMap(fromElement, fromInclusive,
                                          toElement,   toInclusive));
        }
        public NavigableSet<E> headSet(E toElement, boolean inclusive) {
            return new KeySet<>(m.headMap(toElement, inclusive));
        }
        public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
            return new KeySet<>(m.tailMap(fromElement, inclusive));
        }
        public SortedSet<E> subSet(E fromElement, E toElement) {
            return subSet(fromElement, true, toElement, false);
        }
        public SortedSet<E> headSet(E toElement) {
            return headSet(toElement, false);
        }
        public SortedSet<E> tailSet(E fromElement) {
            return tailSet(fromElement, true);
        }
        public NavigableSet<E> descendingSet() {
            return new KeySet(m.descendingMap());
        }
    }

//返回map的逆序視圖
 public NavigableMap<K, V> descendingMap() {
        NavigableMap<K, V> km = descendingMap;
        return (km != null) ? km :
            (descendingMap = new DescendingSubMap(this,
                                                  true, null, true,
                                                  true, null, true));
    }