一、属性

1.1 Entry

static final class Entry<K,V> implements Map.Entry<K,V> {K key;V value;Entry<K,V> left;Entry<K,V> right;Entry<K,V> parent;boolean color = BLACK;/*** Make a new cell with given key, value, and parent, and with* {@code null} child links, and BLACK color.*/Entry(K key, V value, Entry<K,V> parent) {this.key = key;this.value = value;this.parent = parent;}/*** Returns the key.** @return the key*/public K getKey() {return key;}/*** Returns the value associated with the key.** @return the value associated with the key*/public V getValue() {return value;}/*** Replaces the value currently associated with the key with the given* value.** @return the value associated with the key before this method was*         called*/public V setValue(V value) {V oldValue = this.value;this.value = value;return oldValue;}public boolean equals(Object o) {if (!(o instanceof Map.Entry))return false;Map.Entry<?,?> e = (Map.Entry<?,?>)o;return valEquals(key,e.getKey()) && valEquals(value,e.getValue());}public int hashCode() {int keyHash = (key==null ? 0 : key.hashCode());int valueHash = (value==null ? 0 : value.hashCode());return keyHash ^ valueHash;}public String toString() {return key + "=" + value;}}

二、方法

2.1 put

将特定的键值对储存进入map中，如果这个map已经包含了Key，那么更新Value的值，同时会返回这个旧值。如果不包含这个Key，那么返回null，注意返回null还有可能是Key对应的值为null。

/*** @throws ClassCastException if the specified key cannot be compared*         with the keys currently in the map* @throws NullPointerException if the specified key is null*         and this map uses natural ordering, or its comparator*         does not permit null keys*/public V put(K key, V value) {Entry<K,V> t = root;if (t == null) {compare(key, key); // type (and possibly null) checkroot = new Entry<>(key, value, null);size = 1;modCount++;return null;}int cmp;Entry<K,V> parent;// split comparator and comparable pathsComparator<? super K> cpr = comparator;if (cpr != null) {do {parent = t;cmp = cpr.compare(key, t.key);if (cmp < 0)t = t.left;else if (cmp > 0)t = t.right;elsereturn t.setValue(value);} while (t != null);}else {if (key == null)throw new NullPointerException();@SuppressWarnings("unchecked")Comparable<? super K> k = (Comparable<? super K>) key;do {parent = t;cmp = k.compareTo(t.key);if (cmp < 0)t = t.left;else if (cmp > 0)t = t.right;elsereturn t.setValue(value);} while (t != null);}Entry<K,V> e = new Entry<>(key, value, parent);if (cmp < 0)parent.left = e;elseparent.right = e;fixAfterInsertion(e);size++;modCount++;return null;}

2.2 get

返回和特定Key值对应的Value，如果不存在，返回null（注意返回null还有可能是Key对应的Value等于null，可以用containsKey来进行区分）。

/*** @throws ClassCastException if the specified key cannot be compared*         with the keys currently in the map* @throws NullPointerException if the specified key is null*         and this map uses natural ordering, or its comparator*         does not permit null keys*/public V get(Object key) {Entry<K,V> p = getEntry(key);return (p==null ? null : p.value);}

2.2.1 getEntry

返回和Key相对应的map的实体，如果不存在，返回null。

/*** @throws ClassCastException if the specified key cannot be compared*         with the keys currently in the map* @throws NullPointerException if the specified key is null*         and this map uses natural ordering, or its comparator*         does not permit null keys*/final Entry<K,V> getEntry(Object key) {// Offload comparator-based version for sake of performanceif (comparator != null)return getEntryUsingComparator(key);if (key == null)throw new NullPointerException();@SuppressWarnings("unchecked")Comparable<? super K> k = (Comparable<? super K>) key;Entry<K,V> p = root;while (p != null) {int cmp = k.compareTo(p.key);if (cmp < 0)p = p.left;else if (cmp > 0)p = p.right;elsereturn p;}return null;}

2.2.1.1 getEntryUsingComparator

使用Comparator进行判断的版本

/*** Version of getEntry using comparator. Split off from getEntry* for performance. (This is not worth doing for most methods,* that are less dependent on comparator performance, but is* worthwhile here.)*/final Entry<K,V> getEntryUsingComparator(Object key) {@SuppressWarnings("unchecked")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;elsereturn p;}}return null;}

2.3 containsValue

如果有至少一个的Key对应这个Value值，则返回true，这个操作是线性的时间复杂度（意味着要遍历整个树）

    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;}

2.4 getFirstEntry

返回二叉搜索树的最小节点

final Entry<K,V> getFirstEntry() {Entry<K,V> p = root;if (p != null)while (p.left != null)p = p.left;return p;}

2.5 getLastEntry

返回二叉搜索树的最大节点

final Entry<K,V> getLastEntry() {Entry<K,V> p = root;if (p != null)while (p.right != null)p = p.right;return p;}

2.6 remove

如果存在和Key对应的键值对，那么在这个TreeMap中删除这个键值对。返回之前和这个Key对应的Value，如果不存在，返回null（注意返回null也可能是Key对应的Value值为null）

/** @throws ClassCastException if the specified key cannot be compared*         with the keys currently in the map* @throws NullPointerException if the specified key is null*         and this map uses natural ordering, or its comparator*         does not permit null keys*/public V remove(Object key) {Entry<K,V> p = getEntry(key);if (p == null)return null;V oldValue = p.value;deleteEntry(p);return oldValue;}

2.6.1 deleteEntry

    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) {//这里s是p右孩子中最小的节点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);//p只有一个孩子的情况if (replacement != null) {// Link replacement to parentreplacement.parent = p.parent;if (p.parent == null)root = replacement;else if (p == p.parent.left)p.parent.left  = replacement;elsep.parent.right = replacement;//这里做的操作是先删除p，然后调整树// Null out links so they are OK to use by fixAfterDeletion.p.left = p.right = p.parent = null;// Fix replacementif (p.color == BLACK)fixAfterDeletion(replacement);} else if (p.parent == null) { // return if we are the only node.root = null;} else { //p是叶子节点的情况//先调整，再删除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;}}}

2.7 successor

寻找传入节点的后继节点

/*** Returns the successor of the specified Entry, or null if no such.*/static <K,V> TreeMap.Entry<K,V> successor(Entry<K,V> t) {if (t == null)return null;else if (t.right != null) {Entry<K,V> p = t.right;while (p.left != null)p = p.left;return p;} else {Entry<K,V> p = t.parent;Entry<K,V> ch = t;while (p != null && ch == p.right) {ch = p;p = p.parent;}return p;}}

2.8 predecessor

寻找当前节点的前驱节点

 /*** Returns the predecessor of the specified Entry, or null if no such.*/static <K,V> Entry<K,V> predecessor(Entry<K,V> t) {if (t == null)return null;else if (t.left != null) {Entry<K,V> p = t.left;while (p.right != null)p = p.right;return p;} else {Entry<K,V> p = t.parent;Entry<K,V> ch = t;while (p != null && ch == p.left) {ch = p;p = p.parent;}return p;}}

2.9 fixAfterInsertion

/** From CLR */private void fixAfterInsertion(Entry<K,V> x) {x.color = RED;while (x != null && x != root && x.parent.color == RED) {//父节点是爷爷结点的左结点if (parentOf(x) == leftOf(parentOf(parentOf(x)))) {//取得父亲结点的兄弟结点（叔叔结点）Entry<K,V> y = rightOf(parentOf(parentOf(x)));//叔叔结点为红色，此时子节点可左可右if (colorOf(y) == RED) {//将父亲结点和叔叔结点染黑setColor(parentOf(x), BLACK);setColor(y, BLACK);//将爷爷结点染红setColor(parentOf(parentOf(x)), RED);//X回溯至爷爷结点x = parentOf(parentOf(x));} else {//叔叔结点为黑色if (x == rightOf(parentOf(x))) {//X是P的右孩子//x指向px = parentOf(x);//左旋protateLeft(x);}//将P染黑，G染红setColor(parentOf(x), BLACK);setColor(parentOf(parentOf(x)), RED);//右旋GrotateRight(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;}

2.10 fixAfterDeletion

/** From CLR */private void fixAfterDeletion(Entry<K,V> x) {//节点x的颜色为黑while (x != root && colorOf(x) == BLACK) {//当x是左节点时if (x == leftOf(parentOf(x))) {Entry<K,V> sib = rightOf(parentOf(x));//第一种情况，兄弟节点S为红色if (colorOf(sib) == RED) {//将S染黑setColor(sib, BLACK);//将P染红，左旋PsetColor(parentOf(x), RED);rotateLeft(parentOf(x));sib = rightOf(parentOf(x));}//兄弟节点为黑色的情况if (colorOf(leftOf(sib))  == BLACK &&colorOf(rightOf(sib)) == BLACK) {//左侄子和右侄子均为黑色//将S染红setColor(sib, RED);//X回溯至Px = parentOf(x);} else {if (colorOf(rightOf(sib)) == BLACK) {//S为黑色，LN为红色，RN为黑色//将LN染黑setColor(leftOf(sib), BLACK);//将S染红setColor(sib, RED);//右旋SrotateRight(sib);//S指向LNsib = rightOf(parentOf(x));}//第四种情况//S为黑色，P可红可黑，RN为红色，LN可红可黑//将S的颜色设置为与P相同setColor(sib, colorOf(parentOf(x)));//P染黑setColor(parentOf(x), BLACK);//RN染黑setColor(rightOf(sib), BLACK);//左旋ProtateLeft(parentOf(x));//X回溯至根节点x = root;}} else { // symmetricEntry<K,V> sib = leftOf(parentOf(x));if (colorOf(sib) == RED) {setColor(sib, BLACK);setColor(parentOf(x), RED);rotateRight(parentOf(x));sib = leftOf(parentOf(x));}if (colorOf(rightOf(sib)) == BLACK &&colorOf(leftOf(sib)) == BLACK) {setColor(sib, RED);x = parentOf(x);} else {if (colorOf(leftOf(sib)) == BLACK) {setColor(rightOf(sib), BLACK);setColor(sib, RED);rotateLeft(sib);sib = leftOf(parentOf(x));}setColor(sib, colorOf(parentOf(x)));setColor(parentOf(x), BLACK);setColor(leftOf(sib), BLACK);rotateRight(parentOf(x));x = root;}}}//回溯过程，不管X是根节点还是红色节点，均调整为黑色setColor(x, BLACK);}

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