==重点: Key对象只有实现了Comparable接口，数据结构才是有序的，java 的默认数据类型都有实现，自己定义的数据类型，请实现这个接口==
数据结构
采用红黑树的数据结构，具体的数据结构描述可以看这里
image
继承
- 最小化实现接口AbstractMap
- NavigableMap有序Map接口
- Cloneable可复制的接口
- Serializable可序列化接口
public class TreeMap<K,V>
extends AbstractMap<K,V>
implements NavigableMap<K,V>, Cloneable, java.io.Serializable
{}
构造
public class TreeMap<K,V>
extends AbstractMap<K,V>
implements NavigableMap<K,V>, Cloneable, java.io.Serializable
{
//比较器，用于比较节点大小,决定节点在左边还是右边
private final Comparator<? super K> comparator;
//树的根节点
private transient Entry<K,V> root;
//节点数量
private transient int size = 0;
//修改次数，用于判断是否在使用迭代器的同时，修改
private transient int modCount = 0;
//无参数创建，在不提供比较器的情况下，采用Key对象的默认compareTo方法来比较节点大小
public TreeMap() {
comparator = null;
}
//通过比较器创建构建
public TreeMap(Comparator<? super K> comparator) {
this.comparator = comparator;
}
//通过其他map数据结构创建新数据
public TreeMap(Map<? extends K, ? extends V> m) {
comparator = null;
putAll(m);
}
//提供有序的Map数据结构来创建
public TreeMap(SortedMap<K, ? extends V> m) {
comparator = m.comparator();
//注意这里发生异常时，不会向外通知
try {
buildFromSorted(m.size(), m.entrySet().iterator(), null, null);
} catch (java.io.IOException cannotHappen) {
} catch (ClassNotFoundException cannotHappen) {
}
}
}
Entry 节点
由于采用的红黑树结构，它的节点自然也是符合左右子节点引用，父节点引用和节点颜色的特点，成员方法也是简单的常规方法
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;
//默认颜色是黑色的
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;
}
}
红黑树的自我调整
很绕，不要纠结，能看懂就看懂，看不懂，不要牛角尖，知道原理就行了
/** From CLR */
private void fixAfterInsertion(Entry<K,V> x) {
//先将颜色调整为红色
x.color = RED;
//判断条件,是否为空，是否是为根节点，是否是红色
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;
}
put
public V put(K key, V value) {
Entry<K,V> t = root;
//看一下是否是一个空树，如果是，则直接添加
if (t == 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;
Comparator<? super K> cpr = comparator;
//有默认的比较器的话，采用默认的
if (cpr != null) {
//如果对数据结构比较清楚，这里就很简单了，就是在树中查找合适的位置，插入
do {
parent = t;
cmp = cpr.compare(key, t.key);
if (cmp < 0)
t = t.left;
else if (cmp > 0)
t = t.right;
else
return t.setValue(value);
} while (t != null);
}
else {
//非根节点的时候，是不允许key值是null
if (key == null)
throw new NullPointerException();
//使用自带的数据类型的比较器
@SuppressWarnings("unchecked")
Comparable<? super K> k = (Comparable<? super K>) key;
//和上面一样，寻找到树的合适位置
do {
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);
}
//创建节点，并插入到树中
Entry<K,V> e = new Entry<>(key, value, parent);
if (cmp < 0)
parent.left = e;
else
parent.right = e;
//此时可能已经不满足红黑树的条件了，需要重新调整
fixAfterInsertion(e);
size++;
modCount++;
return null;
}
get
基本就是二叉查找的过程，
public V get(Object key) {
Entry<K,V> p = getEntry(key);
return (p==null ? null : p.value);
}
final Entry<K,V> getEntry(Object key) {
//看一下是否要使用默认比较器
if (comparator != null)
return getEntryUsingComparator(key);
//如果没有自定义比较器，使用NULL查找是会报错的
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;
else
return p;
}
return null;
}
//这个是使用默认比较器查找的方式
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;
//这就是一个遍历比较的方法
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;
}
remove
public V remove(Object key) {
//先获取节点
Entry<K,V> p = getEntry(key);
if (p == null)
return null;
V oldValue = p.value;
//删除节点
deleteEntry(p);
return oldValue;
}
private void deleteEntry(Entry<K,V> p) {
modCount++;
size--;
//如果两个子节点都不为空，调整一下两个子节点
if (p.left != null && p.right != null) {
//合并两个子节点
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);
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) { //根节点
root = null;
} else { //如果两个节点都没有
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;
}
}
}
//将两个子节点调整成一颗树
static <K,V> TreeMap.Entry<K,V> successor(Entry<K,V> t) {
//为空的时候
if (t == null)
return null;
//右节点不为空的时候
else if (t.right != null) {
Entry<K,V> p = t.right;
while (p.left != null)
p = p.left;
return p;
//右节点空的时
} 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;
}
}
