第十二章 映射 Map
- Map 在有些编程语言中也叫做字典（dictionary，比如 Python、Objective-C、Swift等）
- Map 中的每一个Key 是唯一的
- Map 中的每一个 Key 对应一个 Value
Map的接口定义
public interface Map<K, V> {
int size();
boolean isEmpty();
void clear();
V put(K key, V value);
V get(K key);
V remove(K key);
boolean containsKey(K key);
boolean containsValue(V value);
void traversal(Visitor<K, V> visitor);
public static abstract class Visitor<K, V> {
boolean stop;
public abstract boolean visit(K key, V value);
}
}
红黑树 RBTree 实现 TreeMap
package cn.xx.java.map;
import java.util.Comparator;
import java.util.LinkedList;
import java.util.Queue;
/**
* @author xiexu
* @create 2021-08-13 10:39 上午
*/
public class TreeMap<K, V> implements Map<K, V> {
private static final boolean RED = false;
private static final boolean BLACK = true;
private int size; //节点数量
private Node<K, V> root; //根节点
private Comparator<K> comparator;
public TreeMap() {
this(null);
}
public TreeMap(Comparator<K> comparator) {
this.comparator = comparator;
}
public int size() {
return size;
}
public boolean isEmpty() {
return size == 0;
}
public void clear() {
root = null;
size = 0;
}
@Override
public V put(K key, V value) {
//判空
keyNotNullCheck(key);
//根节点为空，相当于添加第一个节点
if (root == null) {
root = new Node<>(key, value, null);
size++;
//新添加节点之后的处理
afterPut(root);
return null;
}
//添加的不是第一个节点
//找到父节点
Node<K, V> parent = root;
Node<K, V> node = root;
int cmp = 0;
while (node != null) {
cmp = commpare(key, node.key);
parent = node;
if (cmp > 0) {
node = node.right;
} else if (cmp < 0) {
node = node.left;
} else { //相等就覆盖
node.key = key;
V oldVal = node.value;
node.value = value;
return oldVal;
}
}
//找到父节点，看看插入到父节点的哪个位置
Node<K, V> newNode = new Node<>(key, value, parent); //创建新节点
if (cmp > 0) {
parent.right = newNode;
} else {
parent.left = newNode;
}
size++;
//新添加节点之后的处理
afterPut(newNode);
return null;
}
@Override
public V get(K key) {
Node<K, V> node = node(key);
return node != null ? node.value : null;
}
@Override
public V remove(K key) {
return remove(node(key));
}
@Override
public boolean containsKey(K key) {
return node(key) != null;
}
@Override
public boolean containsValue(V value) {
if (root == null) {
return false;
}
Queue<Node<K, V>> queue = new LinkedList<>();
queue.offer(root);
while (!queue.isEmpty()) {
Node<K, V> node = queue.poll();
if (valEquals(value, node.value)) {
return true;
}
if (node.left != null) {
queue.offer(node.left);
}
if (node.right != null) {
queue.offer(node.right);
}
}
return false;
}
@Override
public void traversal(Visitor<K, V> visitor) {
if (visitor == null) {
return;
}
traversal(root, visitor);
}
private void afterPut(Node<K, V> node) {
Node<K, V> parent = node.parent;
//添加的是根节点或者上溢到达了根节点
if (parent == null) {
black(node); //直接将根节点染成黑色
return;
}
//如果父节点是黑色，则直接返回
if (isBlack(parent)) {
return;
}
//uncle节点
Node<K, V> uncle = parent.sibling();
//grand节点
Node<K, V> grand = parent.parent;
//uncle节点是红色[B树节点上溢]
if (isRed(uncle)) {
black(parent);
black(uncle);
red(grand);
//grand节点当做是新添加的节点
afterPut(grand);
return;
}
//uncle节点不是红色
if (parent.isLeftChild()) { //L
if (node.isLeftChild()) { //LL
black(parent);
red(grand);
rotateRight(grand); //右旋
} else { //LR
black(node);
red(grand);
rotateLeft(parent); //左旋
rotateRight(grand); //右旋
}
} else { //R
if (node.isLeftChild()) { //RL
black(node);
red(grand);
rotateRight(parent); //右旋
rotateLeft(grand); //左旋
} else { //RR
black(parent);
red(grand);
rotateLeft(grand); //左旋
}
}
}
private int commpare(K k1, K k2) {
if (comparator != null) {
return comparator.compare(k1, k2);
} else {
return ((Comparable<K>) k1).compareTo(k2);
}
}
private void keyNotNullCheck(K key) {
if (key == null) {
throw new IllegalArgumentException("element must not be null");
}
}
private V remove(Node<K, V> node) {
if (node == null) {
return null;
}
size--;
V oldValue = node.value;
if (node.hasTwoChildren()) { //度为2的节点
//找到后继节点
Node<K, V> s = successor(node);
//用后继节点的值，覆盖度为2的节点的值
node.key = s.key;
node.value = s.value;
//删除后继节点
node = s;
}
//删除node节点（node的度必然是1或者0）
Node<K, V> replacement = node.left != null ? node.left : node.right;
if (replacement != null) { //node是度为1的节点
//更改parent
replacement.parent = node.parent;
//更改parent的left，right的指向
if (node.parent == null) { //node是度为1的节点并且是根节点
root = replacement;
} else {
if (node == node.parent.left) {
node.parent.left = replacement;
} else { //node == node.parent.right
node.parent.right = replacement;
}
}
//删除节点之后的处理
afterRemove(replacement);
} else if (node.parent == null) { //node是叶子节点并且是根节点
root = null;
} else { //node是叶子节点，但不是根节点
if (node == node.parent.left) {
node.parent.left = null;
} else { //node == node.parent.right
node.parent.right = null;
}
//删除节点之后的处理
afterRemove(node);
}
return oldValue;
}
private void afterRemove(Node<K, V> node) {
//如果删除的节点是红色 或者 用以取代删除节点的子节点是红色
if (isRed(node)) {
black(node);
return;
}
//parent节点
Node<K, V> parent = node.parent;
//删除的是黑色叶子节点[下溢]
//判断被删除的node是左还是右，因为被删除后该父节点的一边就会为空，所以兄弟节点就在另一边
boolean left = parent.left == null || node.isLeftChild();
Node<K, V> sibling = left ? parent.right : parent.left;
if (left) { //被删除的节点在左边，兄弟节点在右边
if (isRed(sibling)) { //兄弟节点是红色
black(sibling); //兄弟节点染成黑色
red(parent); //parent节点染成红色
rotateLeft(parent); //右旋
//更换兄弟
sibling = parent.right;
}
//兄弟节点必然是黑色
//如果左右节点为null，null也是黑色
if (isBlack(sibling.left) && isBlack(sibling.right)) {
//兄弟节点没有一个红色子节点，父节点要向下跟兄弟节点合并
boolean parentBlack = isBlack(parent); //处理之前先检查下父节点是不是黑色
black(parent);
red(sibling);
if (parentBlack) {
//只需把 parent 当做被删除的节点处理即可
afterRemove(parent);
}
} else { //兄弟节点至少有1个红色子节点，向兄弟节点借元素
//兄弟节点的右边是黑色，要对兄弟节点进行左旋转
if (isBlack(sibling.right)) {
rotateRight(sibling);
sibling = parent.right; //兄弟节点要重新赋值
}
//sibling继承parent的颜色
color(sibling, colorOf(parent));
black(sibling.right);
black(parent);
rotateLeft(parent);
}
} else { //被删除的节点在右边，兄弟节点在左边
if (isRed(sibling)) { //兄弟节点是红色
black(sibling); //兄弟节点染成黑色
red(parent); //parent节点染成红色
rotateRight(parent); //右旋
//更换兄弟
sibling = parent.left;
}
//兄弟节点必然是黑色
//如果左右节点为null，null也是黑色
if (isBlack(sibling.left) && isBlack(sibling.right)) {
//兄弟节点没有一个红色子节点，父节点要向下跟兄弟节点合并
boolean parentBlack = isBlack(parent); //处理之前先检查下父节点是不是黑色
black(parent);
red(sibling);
if (parentBlack) {
//只需把 parent 当做被删除的节点处理即可
afterRemove(parent);
}
} else { //兄弟节点至少有1个红色子节点，向兄弟节点借元素
//兄弟节点的左边是黑色，要对兄弟节点进行左旋转
if (isBlack(sibling.left)) {
rotateLeft(sibling);
sibling = parent.left; //兄弟节点要重新赋值
}
//sibling继承parent的颜色
color(sibling, colorOf(parent));
black(sibling.left);
black(parent);
rotateRight(parent);
}
}
}
/**
* 前驱节点: 中序遍历时的前一个节点
* 求前驱节点
*/
private Node<K, V> predecessor(Node<K, V> node) {
if (node == null) {
return null;
}
//前驱节点在左子树中(left.right.right.right....)
Node<K, V> p = node.left;
if (node.left != null) {
//左子树不为空，则找到它的最右节点
while (p.right != null) {
p = p.right;
}
return p;
}
// 能来到这里说明左子树为空, 则从父节点、祖父节点中寻找前驱节点
// 当父节点不为空, 且某节点为父节点的左子节点
// 则顺着父节点找, 直到找到【某结点为父节点或祖父节点的右子树中】时
while (node.parent != null && node.parent.left == node) {
node = node.parent;
}
// 来到这里有以下两种情况:
// node.parent == null 无前驱, 说明是根结点
// node.parent...right == node 找到【某结点为父节点或祖父节点的右子树中】
// 那么父节点就是某节点的前驱节点
return node.parent;
}
/**
* 后继节点: 中序遍历时的后一个节点
* 求后继节点
*/
private Node<K, V> successor(Node<K, V> node) {
if (node == null) {
return null;
}
//后继节点在右子树中(right.left.left.left....)
Node<K, V> p = node.right;
if (node.right != null) {
//左子树不为空，则找到它的最右节点
while (p.left != null) {
p = p.left;
}
return p;
}
// 能来到这里说明右子树为空, 则从父节点、祖父节点中寻找后继节点
// 当父节点不为空, 且某节点为父节点的右子节点
// 则顺着父节点找, 直到找到【某结点为父节点或祖父节点的左子树中】时
while (node.parent != null && node.parent.right == node) {
node = node.parent;
}
// 来到这里有以下两种情况:
// node.parent == null 无后继, 说明是根结点
// node.parent...left == node 找到【某结点为父节点或祖父节点的左子树中】
// 那么父节点就是某节点的后继节点
return node.parent;
}
private void traversal(Node<K, V> node, Visitor<K, V> visitor) {
if (node == null || visitor.stop) {
return;
}
traversal(node.left, visitor);
if (visitor.stop) {
return;
}
visitor.visit(node.key, node.value);
traversal(node.right, visitor);
}
private boolean valEquals(V v1, V v2) {
return v1 == null ? v2 == null : v1.equals(v2);
}
/**
* 给节点染色
*
* @param node
* @param color
* @return
*/
private Node<K, V> color(Node<K, V> node, boolean color) {
if (node == null) {
return node;
}
node.color = color;
return node;
}
/**
* 把节点染成红色
*
* @param node
* @return
*/
private Node<K, V> red(Node<K, V> node) {
return color(node, RED);
}
/**
* 把节点染成黑色
*
* @param node
* @return
*/
private Node<K, V> black(Node<K, V> node) {
return color(node, BLACK);
}
/**
* 判断当前节点是什么颜色的
* 空节点默认是黑色
*
* @param node
* @return
*/
private boolean colorOf(Node<K, V> node) {
return node == null ? BLACK : node.color;
}
/**
* 当前节点是否为黑色
*
* @param node
* @return
*/
private boolean isBlack(Node<K, V> node) {
return colorOf(node) == BLACK;
}
/**
* 当前节点是否为红色
*
* @param node
* @return
*/
private boolean isRed(Node<K, V> node) {
return colorOf(node) == RED;
}
/**
* 左旋
*
* @param grand
*/
private void rotateLeft(Node<K, V> grand) {
Node<K, V> parent = grand.right;
Node<K, V> child = parent.left;
grand.right = child;
parent.left = grand;
afterRotate(grand, parent, child);
}
/**
* 右旋
*
* @param grand
*/
private void rotateRight(Node<K, V> grand) {
Node<K, V> parent = grand.left;
Node<K, V> child = parent.right;
grand.left = child;
parent.right = grand;
afterRotate(grand, parent, child);
}
/**
* 公共代码：不管是左旋转、右旋转，都要执行
*
* @param grand 失衡节点
* @param parent
* @param child
*/
private void afterRotate(Node<K, V> grand, Node<K, V> parent, Node<K, V> child) {
//让parent成为子树的根节点
parent.parent = grand.parent;
if (grand.isLeftChild()) {
grand.parent.left = parent;
} else if (grand.isRightChild()) {
grand.parent.right = parent;
} else { //grand是根节点
root = parent;
}
//更新child的parent
if (child != null) {
child.parent = grand;
}
//更新grand的parent
grand.parent = parent;
}
private Node<K, V> node(K key) {
Node<K, V> node = root;
while (node != null) {
int cmp = commpare(key, node.key);
if (cmp == 0) {
return node;
} else if (cmp > 0) {
node = node.right;
} else { //cmp < 0
node = node.left;
}
}
return null;
}
private static class Node<K, V> {
K key;
V value;
boolean color;
Node<K, V> left; //左子节点
Node<K, V> right; //右子节点
Node<K, V> parent; //父节点
public Node(K key, V value, Node<K, V> parent) {
this.key = key;
this.value = value;
this.parent = parent;
}
//判断当前节点是不是叶子节点
public boolean isLeaf() {
return left == null && right == null;
}
//判断当前节点是不是拥有两个子节点
public boolean hasTwoChildren() {
return left != null && right != null;
}
//判断当前节点是不是左子树
public boolean isLeftChild() {
return parent != null && this == parent.left;
}
//判断当前节点是不是右子树
public boolean isRightChild() {
return parent != null && this == parent.right;
}
//返回兄弟结点
public Node<K, V> sibling() {
if (isLeftChild()) {
return parent.right;
}
if (isRightChild()) {
return parent.left;
}
return null;
}
}
}
TreeMap 分析
- Map 中存储的元素不需要讲究顺序
- Map 中的 Key 不需要具备可比较性
- 不考虑顺序、不考虑 Key 的可比较性，Map 有更好的实现方案，平均时间复杂度可以达到 O( 1 )
哈希表实现 HashMap
package cn.xx.java.map;package cn.xx.java.map;
import cn.xx.java.printer.BinaryTreeInfo;
import cn.xx.java.printer.BinaryTrees;
import java.util.LinkedList;
import java.util.Objects;
import java.util.Queue;
/**
* @author xiexu
* @create 2021-08-15 5:18 下午
*/
public class HashMap<K, V> implements Map<K, V> {
private static final boolean RED = false;
private static final boolean BLACK = true;
private int size;
private Node<K, V>[] table;
private static final int DEFAULT_CAPACITY = 1 << 4;
private static final float DEFAULT_LOAD_FACTOR = 0.75f;
public HashMap() {
table = new Node[DEFAULT_CAPACITY]; //数组默认容量是16
}
@Override
public int size() {
return size;
}
@Override
public boolean isEmpty() {
return size == 0;
}
@Override
public void clear() {
if (size == 0) { //size等于0，就没必要去遍历数组
return;
}
size = 0;
for (int i = 0; i < table.length; i++) {
table[i] = null;
}
}
@Override
public V put(K key, V value) {
resize();
int index = index(key);
//取出index位置的红黑树根节点
Node<K, V> root = table[index];
if (root == null) {
root = createNode(key, value, null);
table[index] = root;
size++;
fixAfterPut(root);
return null;
}
//添加的不是第一个节点
//添加新的节点到红黑树上面
//找到父节点
Node<K, V> parent = root;
Node<K, V> node = root;
int cmp = 0;
K k1 = key;
int h1 = hash(k1);
Node<K, V> result = null;
boolean searched = false; //是否已经搜索过这个key
do {
parent = node;
K k2 = node.key;
int h2 = node.hash;
if (h1 > h2) {
cmp = 1;
} else if (h1 < h2) {
cmp = -1;
} else if (Objects.equals(k1, k2)) {
cmp = 0;
} else if (k1 != null && k2 != null
&& k1.getClass() == k2.getClass()
&& k1 instanceof Comparable
&& (cmp = ((Comparable) k1).compareTo(k2)) != 0) {
} else if (searched) { //已经扫描了
cmp = System.identityHashCode(k1) - System.identityHashCode(k2);
} else { //searched == false 还没有扫描，再根据内存地址大小决定左右
if (node.left != null && (result = node(node.left, k1)) != null
|| node.right != null && (result = node(node.right, k1)) != null) {
//已经存在这个key
node = result;
cmp = 0;
} else { //不存在这个key
searched = true;
cmp = System.identityHashCode(k1) - System.identityHashCode(k2);
}
}
if (cmp > 0) {
node = node.right;
} else if (cmp < 0) {
node = node.left;
} else { //相等就覆盖
V oldValue = node.value;
node.key = key;
node.value = value;
node.hash = h1;
return oldValue;
}
} while (node != null);
//找到父节点，看看插入到父节点的哪个位置
Node<K, V> newNode = createNode(key, value, parent); //创建新节点
if (cmp > 0) {
parent.right = newNode;
} else {
parent.left = newNode;
}
size++;
//新添加节点之后的处理
fixAfterPut(newNode);
return null;
}
protected Node<K, V> createNode(K key, V value, Node<K, V> parent) {
return new Node<>(key, value, parent);
}
private void resize() {
//负载因子 <= 0.75
if (size / table.length <= DEFAULT_LOAD_FACTOR) {
return;
}
Node<K, V>[] oldTable = table;
table = new Node[oldTable.length << 1]; //扩容为原来的2倍
Queue<Node<K, V>> queue = new LinkedList<>();
for (int i = 0; i < oldTable.length; i++) {
if (oldTable[i] == null) {
continue;
}
queue.offer(oldTable[i]);
while (!queue.isEmpty()) {
Node<K, V> node = queue.poll();
if (node.left != null) {
queue.offer(node.left);
}
if (node.right != null) {
queue.offer(node.right);
}
//挪动代码得放在最后面
moveNode(node);
}
}
}
private void moveNode(Node<K, V> newNode) {
//重置node的关系
newNode.parent = null;
newNode.left = null;
newNode.right = null;
newNode.color = RED;
int index = index(newNode);
//取出index位置的红黑树根节点
Node<K, V> root = table[index];
if (root == null) {
root = newNode;
table[index] = root;
fixAfterPut(root);
return;
}
//添加的不是第一个节点
//添加新的节点到红黑树上面
//找到父节点
Node<K, V> parent = root;
Node<K, V> node = root;
int cmp = 0;
K k1 = newNode.key;
int h1 = newNode.hash;
do {
parent = node;
K k2 = node.key;
int h2 = node.hash;
if (h1 > h2) {
cmp = 1;
} else if (h1 < h2) {
cmp = -1;
} else if (k1 != null && k2 != null
&& k1.getClass() == k2.getClass()
&& k1 instanceof Comparable
&& (cmp = ((Comparable) k1).compareTo(k2)) != 0) {
} else {
cmp = System.identityHashCode(k1) - System.identityHashCode(k2);
}
if (cmp > 0) {
node = node.right;
} else if (cmp < 0) {
node = node.left;
}
} while (node != null);
//找到父节点，看看插入到父节点的哪个位置
newNode.parent = parent;
if (cmp > 0) {
parent.right = newNode;
} else {
parent.left = newNode;
}
//新添加节点之后的处理
fixAfterPut(newNode);
}
@Override
public V get(K key) {
Node<K, V> node = node(key);
return node != null ? node.value : null;
}
@Override
public V remove(K key) {
return remove(node(key));
}
@Override
public boolean containsKey(K key) {
return node(key) != null;
}
@Override
public boolean containsValue(V value) {
if (size == 0) {
return false;
}
Queue<Node<K, V>> queue = new LinkedList<>();
for (int i = 0; i < table.length; i++) {
if (table[i] == null) {
continue;
}
queue.offer(table[i]);
while (!queue.isEmpty()) {
Node<K, V> node = queue.poll();
if (Objects.equals(value, node.value)) {
return true;
}
if (node.left != null) {
queue.offer(node.left);
}
if (node.right != null) {
queue.offer(node.right);
}
}
}
return false;
}
@Override
public void traversal(Visitor<K, V> visitor) {
if (size == 0 || visitor == null) {
return;
}
Queue<Node<K, V>> queue = new LinkedList<>();
for (int i = 0; i < table.length; i++) {
if (table[i] == null) {
continue;
}
queue.offer(table[i]);
while (!queue.isEmpty()) {
Node<K, V> node = queue.poll();
if (visitor.visit(node.key, node.value)) {
return;
}
if (node.left != null) {
queue.offer(node.left);
}
if (node.right != null) {
queue.offer(node.right);
}
}
}
}
public void print() {
if (size == 0) {
return;
}
for (int i = 0; i < table.length; i++) {
final Node<K, V> root = table[i];
System.out.println("[index = " + i + "]");
BinaryTrees.println(new BinaryTreeInfo() {
@Override
public Object string(Object node) {
return node;
}
@Override
public Object root() {
return root;
}
@Override
public Object right(Object node) {
return ((Node<K, V>) node).right;
}
@Override
public Object left(Object node) {
return ((Node<K, V>) node).left;
}
});
System.out.println("-----------------------------------");
}
}
private V remove(Node<K, V> node) {
if (node == null) {
return null;
}
size--;
V oldValue = node.value;
if (node.hasTwoChildren()) { //度为2的节点
//找到后继节点
Node<K, V> s = successor(node);
//用后继节点的值，覆盖度为2的节点的值
node.key = s.key;
node.value = s.value;
node.hash = s.hash;
//删除后继节点
node = s;
}
//删除node节点（node的度必然是1或者0）
Node<K, V> replacement = node.left != null ? node.left : node.right;
int index = index(node);
if (replacement != null) { //node是度为1的节点
//更改parent
replacement.parent = node.parent;
//更改parent的left，right的指向
if (node.parent == null) { //node是度为1的节点并且是根节点
table[index] = replacement;
} else {
if (node == node.parent.left) {
node.parent.left = replacement;
} else { //node == node.parent.right
node.parent.right = replacement;
}
}
//删除节点之后的处理
fixAfterRemove(replacement);
} else if (node.parent == null) { //node是叶子节点并且是根节点
table[index] = null;
} else { //node是叶子节点，但不是根节点
if (node == node.parent.left) {
node.parent.left = null;
} else { //node == node.parent.right
node.parent.right = null;
}
//删除节点之后的处理
fixAfterRemove(node);
}
return oldValue;
}
/**
* 后继节点: 中序遍历时的后一个节点
* 求后继节点
*/
private Node<K, V> successor(Node<K, V> node) {
if (node == null) {
return null;
}
//后继节点在右子树中(right.left.left.left....)
Node<K, V> p = node.right;
if (node.right != null) {
//左子树不为空，则找到它的最右节点
while (p.left != null) {
p = p.left;
}
return p;
}
// 能来到这里说明右子树为空, 则从父节点、祖父节点中寻找后继节点
// 当父节点不为空, 且某节点为父节点的右子节点
// 则顺着父节点找, 直到找到【某结点为父节点或祖父节点的左子树中】时
while (node.parent != null && node.parent.right == node) {
node = node.parent;
}
// 来到这里有以下两种情况:
// node.parent == null 无后继, 说明是根结点
// node.parent...left == node 找到【某结点为父节点或祖父节点的左子树中】
// 那么父节点就是某节点的后继节点
return node.parent;
}
private Node<K, V> node(K key) {
Node<K, V> root = table[index(key)];
return root == null ? null : node(root, key);
}
private Node<K, V> node(Node<K, V> node, K k1) {
int h1 = hash(k1);
//存储查找结果
Node<K, V> result = null;
int cmp = 0;
while (node != null) {
int h2 = node.hash;
K k2 = node.key;
//先比较哈希值
if (h1 > h2) {
node = node.right;
} else if (h1 < h2) {
node = node.left;
} else if (Objects.equals(k1, k2)) {
return node;
} else if (k1 != null && k2 != null
&& k1.getClass() == k2.getClass()
&& k1 instanceof Comparable
&& (cmp = ((Comparable) k1).compareTo(k2)) != 0) {
node = cmp > 0 ? node.right : node.left;
} else if (node.right != null && (result = node(node.right, k1)) != null) {
return result;
} else { //只能往左边找
node = node.left;
}
}
return null;
}
/**
* 根据key生成对应的索引（在桶数组中的位置）
*
* @param key
* @return
*/
private int index(K key) {
return hash(key) & (table.length - 1);
}
private int hash(K key) {
//如果key等于null，直接放在数组索引为0的位置
if (key == null) {
return 0;
}
int hash = key.hashCode();
return hash ^ (hash >>> 16);
}
private int index(Node<K, V> node) {
return node.hash & (table.length - 1);
}
private void fixAfterPut(Node<K, V> node) {
Node<K, V> parent = node.parent;
//添加的是根节点 或者 上溢到达了根节点
if (parent == null) {
black(node); //直接将根节点染成黑色
return;
}
//如果父节点是黑色，则直接返回
if (isBlack(parent)) {
return;
}
//uncle节点
Node<K, V> uncle = parent.sibling();
//grand节点
Node<K, V> grand = parent.parent;
//uncle节点是红色[B树节点上溢]
if (isRed(uncle)) {
black(parent);
black(uncle);
red(grand);
//grand节点当做是新添加的节点
fixAfterPut(grand);
return;
}
//uncle节点不是红色
if (parent.isLeftChild()) { //L
if (node.isLeftChild()) { //LL
black(parent);
red(grand);
rotateRight(grand); //右旋
} else { //LR
black(node);
red(grand);
rotateLeft(parent); //左旋
rotateRight(grand); //右旋
}
} else { //R
if (node.isLeftChild()) { //RL
black(node);
red(grand);
rotateRight(parent); //右旋
rotateLeft(grand); //左旋
} else { //RR
black(parent);
red(grand);
rotateLeft(grand); //左旋
}
}
}
private void fixAfterRemove(Node<K, V> node) {
//如果删除的节点是红色 或者 用以取代删除节点的子节点是红色
if (isRed(node)) {
black(node);
return;
}
//parent节点
Node<K, V> parent = node.parent;
//删除的是根节点
if (parent == null) {
return;
}
//删除的是黑色叶子节点[下溢]
//判断被删除的node是左还是右，因为被删除后该父节点的一边就会为空，所以兄弟节点就在另一边
boolean left = parent.left == null || node.isLeftChild();
Node<K, V> sibling = left ? parent.right : parent.left;
if (left) { //被删除的节点在左边，兄弟节点在右边
if (isRed(sibling)) { //兄弟节点是红色
black(sibling); //兄弟节点染成黑色
red(parent); //parent节点染成红色
rotateLeft(parent); //右旋
//更换兄弟
sibling = parent.right;
}
//兄弟节点必然是黑色
//如果左右节点为null，null也是黑色
if (isBlack(sibling.left) && isBlack(sibling.right)) {
//兄弟节点没有一个红色子节点，父节点要向下跟兄弟节点合并
boolean parentBlack = isBlack(parent); //处理之前先检查下父节点是不是黑色
black(parent);
red(sibling);
if (parentBlack) {
//只需把 parent 当做被删除的节点处理即可
fixAfterRemove(parent);
}
} else { //兄弟节点至少有1个红色子节点，向兄弟节点借元素
//兄弟节点的右边是黑色，要对兄弟节点进行左旋转
if (isBlack(sibling.right)) {
rotateRight(sibling);
sibling = parent.right; //兄弟节点要重新赋值
}
//sibling继承parent的颜色
color(sibling, colorOf(parent));
black(sibling.right);
black(parent);
rotateLeft(parent);
}
} else { //被删除的节点在右边，兄弟节点在左边
if (isRed(sibling)) { //兄弟节点是红色
black(sibling); //兄弟节点染成黑色
red(parent); //parent节点染成红色
rotateRight(parent); //右旋
//更换兄弟
sibling = parent.left;
}
//兄弟节点必然是黑色
//如果左右节点为null，null也是黑色
if (isBlack(sibling.left) && isBlack(sibling.right)) {
//兄弟节点没有一个红色子节点，父节点要向下跟兄弟节点合并
boolean parentBlack = isBlack(parent); //处理之前先检查下父节点是不是黑色
black(parent);
red(sibling);
if (parentBlack) {
//只需把 parent 当做被删除的节点处理即可
fixAfterRemove(parent);
}
} else { //兄弟节点至少有1个红色子节点，向兄弟节点借元素
//兄弟节点的左边是黑色，要对兄弟节点进行左旋转
if (isBlack(sibling.left)) {
rotateLeft(sibling);
sibling = parent.left; //兄弟节点要重新赋值
}
//sibling继承parent的颜色
color(sibling, colorOf(parent));
black(sibling.left);
black(parent);
rotateRight(parent);
}
}
}
/**
* 左旋
*
* @param grand
*/
private void rotateLeft(Node<K, V> grand) {
Node<K, V> parent = grand.right;
Node<K, V> child = parent.left;
grand.right = child;
parent.left = grand;
afterRotate(grand, parent, child);
}
/**
* 右旋
*
* @param grand
*/
private void rotateRight(Node<K, V> grand) {
Node<K, V> parent = grand.left;
Node<K, V> child = parent.right;
grand.left = child;
parent.right = grand;
afterRotate(grand, parent, child);
}
/**
* 公共代码：不管是左旋转、右旋转，都要执行
*
* @param grand 失衡节点
* @param parent
* @param child
*/
private void afterRotate(Node<K, V> grand, Node<K, V> parent, Node<K, V> child) {
//让parent成为子树的根节点
parent.parent = grand.parent;
if (grand.isLeftChild()) {
grand.parent.left = parent;
} else if (grand.isRightChild()) {
grand.parent.right = parent;
} else { //grand是根节点
table[index(grand)] = parent;
}
//更新child的parent
if (child != null) {
child.parent = grand;
}
//更新grand的parent
grand.parent = parent;
}
/**
* 给节点染色
*
* @param node
* @param color
* @return
*/
private Node<K, V> color(Node<K, V> node, boolean color) {
if (node == null) {
return node;
}
node.color = color;
return node;
}
/**
* 把节点染成红色
*
* @param node
* @return
*/
private Node<K, V> red(Node<K, V> node) {
return color(node, RED);
}
/**
* 把节点染成黑色
*
* @param node
* @return
*/
private Node<K, V> black(Node<K, V> node) {
return color(node, BLACK);
}
/**
* 判断当前节点是什么颜色的
* 空节点默认是黑色
*
* @param node
* @return
*/
private boolean colorOf(Node<K, V> node) {
return node == null ? BLACK : node.color;
}
/**
* 当前节点是否为黑色
*
* @param node
* @return
*/
private boolean isBlack(Node<K, V> node) {
return colorOf(node) == BLACK;
}
/**
* 当前节点是否为红色
*
* @param node
* @return
*/
private boolean isRed(Node<K, V> node) {
return colorOf(node) == RED;
}
private static class Node<K, V> {
int hash;
K key;
V value;
boolean color;
Node<K, V> left; //左子节点
Node<K, V> right; //右子节点
Node<K, V> parent; //父节点
public Node(K key, V value, Node<K, V> parent) {
this.key = key;
int hash = key == null ? 0 : key.hashCode();
this.hash = hash ^ (hash >>> 16);
this.value = value;
this.parent = parent;
}
//判断当前节点是不是叶子节点
public boolean isLeaf() {
return left == null && right == null;
}
//判断当前节点是不是拥有两个子节点
public boolean hasTwoChildren() {
return left != null && right != null;
}
//判断当前节点是不是左子树
public boolean isLeftChild() {
return parent != null && this == parent.left;
}
//判断当前节点是不是右子树
public boolean isRightChild() {
return parent != null && this == parent.right;
}
//返回兄弟结点
public Node<K, V> sibling() {
if (isLeftChild()) {
return parent.right;
}
if (isRightChild()) {
return parent.left;
}
return null;
}
@Override
public String toString() {
return "Node_" + key + "_" + value;
}
}
}
import cn.xx.java.printer.BinaryTreeInfo;
import cn.xx.java.printer.BinaryTrees;
import java.util.LinkedList;
import java.util.Objects;
import java.util.Queue;
/**
* @author xiexu
* @create 2021-08-15 5:18 下午
*/
public class HashMap<K, V> implements Map<K, V> {
private static final boolean RED = false;
private static final boolean BLACK = true;
private int size;
private Node<K, V>[] table;
private static final int DEFAULT_CAPACITY = 1 << 4;
private static final float DEFAULT_LOAD_FACTOR = 0.75f;
public HashMap() {
table = new Node[DEFAULT_CAPACITY]; //数组默认容量是16
}
@Override
public int size() {
return size;
}
@Override
public boolean isEmpty() {
return size == 0;
}
@Override
public void clear() {
if (size == 0) { //size等于0，就没必要去遍历数组
return;
}
size = 0;
for (int i = 0; i < table.length; i++) {
table[i] = null;
}
}
@Override
public V put(K key, V value) {
resize();
int index = index(key);
//取出index位置的红黑树根节点
Node<K, V> root = table[index];
if (root == null) {
root = createNode(key, value, null);
table[index] = root;
size++;
fixAfterPut(root);
return null;
}
//添加的不是第一个节点
//添加新的节点到红黑树上面
//找到父节点
Node<K, V> parent = root;
Node<K, V> node = root;
int cmp = 0;
K k1 = key;
int h1 = hash(k1);
Node<K, V> result = null;
boolean searched = false; //是否已经搜索过这个key
do {
parent = node;
K k2 = node.key;
int h2 = node.hash;
if (h1 > h2) {
cmp = 1;
} else if (h1 < h2) {
cmp = -1;
} else if (Objects.equals(k1, k2)) {
cmp = 0;
} else if (k1 != null && k2 != null
&& k1.getClass() == k2.getClass()
&& k1 instanceof Comparable
&& (cmp = ((Comparable) k1).compareTo(k2)) != 0) {
} else if (searched) { //已经扫描了
cmp = System.identityHashCode(k1) - System.identityHashCode(k2);
} else { //searched == false 还没有扫描，再根据内存地址大小决定左右
if (node.left != null && (result = node(node.left, k1)) != null
|| node.right != null && (result = node(node.right, k1)) != null) {
//已经存在这个key
node = result;
cmp = 0;
} else { //不存在这个key
searched = true;
cmp = System.identityHashCode(k1) - System.identityHashCode(k2);
}
}
if (cmp > 0) {
node = node.right;
} else if (cmp < 0) {
node = node.left;
} else { //相等就覆盖
V oldValue = node.value;
node.key = key;
node.value = value;
node.hash = h1;
return oldValue;
}
} while (node != null);
//找到父节点，看看插入到父节点的哪个位置
Node<K, V> newNode = createNode(key, value, parent); //创建新节点
if (cmp > 0) {
parent.right = newNode;
} else {
parent.left = newNode;
}
size++;
//新添加节点之后的处理
fixAfterPut(newNode);
return null;
}
protected Node<K, V> createNode(K key, V value, Node<K, V> parent) {
return new Node<>(key, value, parent);
}
private void resize() {
//负载因子 <= 0.75
if (size / table.length <= DEFAULT_LOAD_FACTOR) {
return;
}
Node<K, V>[] oldTable = table;
table = new Node[oldTable.length << 1]; //扩容为原来的2倍
Queue<Node<K, V>> queue = new LinkedList<>();
for (int i = 0; i < oldTable.length; i++) {
if (oldTable[i] == null) {
continue;
}
queue.offer(oldTable[i]);
while (!queue.isEmpty()) {
Node<K, V> node = queue.poll();
if (node.left != null) {
queue.offer(node.left);
}
if (node.right != null) {
queue.offer(node.right);
}
//挪动代码得放在最后面
moveNode(node);
}
}
}
private void moveNode(Node<K, V> newNode) {
//重置node的关系
newNode.parent = null;
newNode.left = null;
newNode.right = null;
newNode.color = RED;
int index = index(newNode);
//取出index位置的红黑树根节点
Node<K, V> root = table[index];
if (root == null) {
root = newNode;
table[index] = root;
fixAfterPut(root);
return;
}
//添加的不是第一个节点
//添加新的节点到红黑树上面
//找到父节点
Node<K, V> parent = root;
Node<K, V> node = root;
int cmp = 0;
K k1 = newNode.key;
int h1 = newNode.hash;
do {
parent = node;
K k2 = node.key;
int h2 = node.hash;
if (h1 > h2) {
cmp = 1;
} else if (h1 < h2) {
cmp = -1;
} else if (k1 != null && k2 != null
&& k1.getClass() == k2.getClass()
&& k1 instanceof Comparable
&& (cmp = ((Comparable) k1).compareTo(k2)) != 0) {
} else {
cmp = System.identityHashCode(k1) - System.identityHashCode(k2);
}
if (cmp > 0) {
node = node.right;
} else if (cmp < 0) {
node = node.left;
}
} while (node != null);
//找到父节点，看看插入到父节点的哪个位置
newNode.parent = parent;
if (cmp > 0) {
parent.right = newNode;
} else {
parent.left = newNode;
}
//新添加节点之后的处理
fixAfterPut(newNode);
}
@Override
public V get(K key) {
Node<K, V> node = node(key);
return node != null ? node.value : null;
}
@Override
public V remove(K key) {
return remove(node(key));
}
@Override
public boolean containsKey(K key) {
return node(key) != null;
}
@Override
public boolean containsValue(V value) {
if (size == 0) {
return false;
}
Queue<Node<K, V>> queue = new LinkedList<>();
for (int i = 0; i < table.length; i++) {
if (table[i] == null) {
continue;
}
queue.offer(table[i]);
while (!queue.isEmpty()) {
Node<K, V> node = queue.poll();
if (Objects.equals(value, node.value)) {
return true;
}
if (node.left != null) {
queue.offer(node.left);
}
if (node.right != null) {
queue.offer(node.right);
}
}
}
return false;
}
@Override
public void traversal(Visitor<K, V> visitor) {
if (size == 0 || visitor == null) {
return;
}
Queue<Node<K, V>> queue = new LinkedList<>();
for (int i = 0; i < table.length; i++) {
if (table[i] == null) {
continue;
}
queue.offer(table[i]);
while (!queue.isEmpty()) {
Node<K, V> node = queue.poll();
if (visitor.visit(node.key, node.value)) {
return;
}
if (node.left != null) {
queue.offer(node.left);
}
if (node.right != null) {
queue.offer(node.right);
}
}
}
}
public void print() {
if (size == 0) {
return;
}
for (int i = 0; i < table.length; i++) {
final Node<K, V> root = table[i];
System.out.println("[index = " + i + "]");
BinaryTrees.println(new BinaryTreeInfo() {
@Override
public Object string(Object node) {
return node;
}
@Override
public Object root() {
return root;
}
@Override
public Object right(Object node) {
return ((Node<K, V>) node).right;
}
@Override
public Object left(Object node) {
return ((Node<K, V>) node).left;
}
});
System.out.println("-----------------------------------");
}
}
private V remove(Node<K, V> node) {
if (node == null) {
return null;
}
size--;
V oldValue = node.value;
if (node.hasTwoChildren()) { //度为2的节点
//找到后继节点
Node<K, V> s = successor(node);
//用后继节点的值，覆盖度为2的节点的值
node.key = s.key;
node.value = s.value;
node.hash = s.hash;
//删除后继节点
node = s;
}
//删除node节点（node的度必然是1或者0）
Node<K, V> replacement = node.left != null ? node.left : node.right;
int index = index(node);
if (replacement != null) { //node是度为1的节点
//更改parent
replacement.parent = node.parent;
//更改parent的left，right的指向
if (node.parent == null) { //node是度为1的节点并且是根节点
table[index] = replacement;
} else {
if (node == node.parent.left) {
node.parent.left = replacement;
} else { //node == node.parent.right
node.parent.right = replacement;
}
}
//删除节点之后的处理
fixAfterRemove(replacement);
} else if (node.parent == null) { //node是叶子节点并且是根节点
table[index] = null;
} else { //node是叶子节点，但不是根节点
if (node == node.parent.left) {
node.parent.left = null;
} else { //node == node.parent.right
node.parent.right = null;
}
//删除节点之后的处理
fixAfterRemove(node);
}
return oldValue;
}
/**
* 后继节点: 中序遍历时的后一个节点
* 求后继节点
*/
private Node<K, V> successor(Node<K, V> node) {
if (node == null) {
return null;
}
//后继节点在右子树中(right.left.left.left....)
Node<K, V> p = node.right;
if (node.right != null) {
//左子树不为空，则找到它的最右节点
while (p.left != null) {
p = p.left;
}
return p;
}
// 能来到这里说明右子树为空, 则从父节点、祖父节点中寻找后继节点
// 当父节点不为空, 且某节点为父节点的右子节点
// 则顺着父节点找, 直到找到【某结点为父节点或祖父节点的左子树中】时
while (node.parent != null && node.parent.right == node) {
node = node.parent;
}
// 来到这里有以下两种情况:
// node.parent == null 无后继, 说明是根结点
// node.parent...left == node 找到【某结点为父节点或祖父节点的左子树中】
// 那么父节点就是某节点的后继节点
return node.parent;
}
private Node<K, V> node(K key) {
Node<K, V> root = table[index(key)];
return root == null ? null : node(root, key);
}
private Node<K, V> node(Node<K, V> node, K k1) {
int h1 = hash(k1);
//存储查找结果
Node<K, V> result = null;
int cmp = 0;
while (node != null) {
int h2 = node.hash;
K k2 = node.key;
//先比较哈希值
if (h1 > h2) {
node = node.right;
} else if (h1 < h2) {
node = node.left;
} else if (Objects.equals(k1, k2)) {
return node;
} else if (k1 != null && k2 != null
&& k1.getClass() == k2.getClass()
&& k1 instanceof Comparable
&& (cmp = ((Comparable) k1).compareTo(k2)) != 0) {
node = cmp > 0 ? node.right : node.left;
} else if (node.right != null && (result = node(node.right, k1)) != null) {
return result;
} else { //只能往左边找
node = node.left;
}
}
return null;
}
/**
* 根据key生成对应的索引（在桶数组中的位置）
*
* @param key
* @return
*/
private int index(K key) {
return hash(key) & (table.length - 1);
}
private int hash(K key) {
//如果key等于null，直接放在数组索引为0的位置
if (key == null) {
return 0;
}
int hash = key.hashCode();
return hash ^ (hash >>> 16);
}
private int index(Node<K, V> node) {
return node.hash & (table.length - 1);
}
private void fixAfterPut(Node<K, V> node) {
Node<K, V> parent = node.parent;
//添加的是根节点 或者 上溢到达了根节点
if (parent == null) {
black(node); //直接将根节点染成黑色
return;
}
//如果父节点是黑色，则直接返回
if (isBlack(parent)) {
return;
}
//uncle节点
Node<K, V> uncle = parent.sibling();
//grand节点
Node<K, V> grand = parent.parent;
//uncle节点是红色[B树节点上溢]
if (isRed(uncle)) {
black(parent);
black(uncle);
red(grand);
//grand节点当做是新添加的节点
fixAfterPut(grand);
return;
}
//uncle节点不是红色
if (parent.isLeftChild()) { //L
if (node.isLeftChild()) { //LL
black(parent);
red(grand);
rotateRight(grand); //右旋
} else { //LR
black(node);
red(grand);
rotateLeft(parent); //左旋
rotateRight(grand); //右旋
}
} else { //R
if (node.isLeftChild()) { //RL
black(node);
red(grand);
rotateRight(parent); //右旋
rotateLeft(grand); //左旋
} else { //RR
black(parent);
red(grand);
rotateLeft(grand); //左旋
}
}
}
private void fixAfterRemove(Node<K, V> node) {
//如果删除的节点是红色 或者 用以取代删除节点的子节点是红色
if (isRed(node)) {
black(node);
return;
}
//parent节点
Node<K, V> parent = node.parent;
//删除的是根节点
if (parent == null) {
return;
}
//删除的是黑色叶子节点[下溢]
//判断被删除的node是左还是右，因为被删除后该父节点的一边就会为空，所以兄弟节点就在另一边
boolean left = parent.left == null || node.isLeftChild();
Node<K, V> sibling = left ? parent.right : parent.left;
if (left) { //被删除的节点在左边，兄弟节点在右边
if (isRed(sibling)) { //兄弟节点是红色
black(sibling); //兄弟节点染成黑色
red(parent); //parent节点染成红色
rotateLeft(parent); //右旋
//更换兄弟
sibling = parent.right;
}
//兄弟节点必然是黑色
//如果左右节点为null，null也是黑色
if (isBlack(sibling.left) && isBlack(sibling.right)) {
//兄弟节点没有一个红色子节点，父节点要向下跟兄弟节点合并
boolean parentBlack = isBlack(parent); //处理之前先检查下父节点是不是黑色
black(parent);
red(sibling);
if (parentBlack) {
//只需把 parent 当做被删除的节点处理即可
fixAfterRemove(parent);
}
} else { //兄弟节点至少有1个红色子节点，向兄弟节点借元素
//兄弟节点的右边是黑色，要对兄弟节点进行左旋转
if (isBlack(sibling.right)) {
rotateRight(sibling);
sibling = parent.right; //兄弟节点要重新赋值
}
//sibling继承parent的颜色
color(sibling, colorOf(parent));
black(sibling.right);
black(parent);
rotateLeft(parent);
}
} else { //被删除的节点在右边，兄弟节点在左边
if (isRed(sibling)) { //兄弟节点是红色
black(sibling); //兄弟节点染成黑色
red(parent); //parent节点染成红色
rotateRight(parent); //右旋
//更换兄弟
sibling = parent.left;
}
//兄弟节点必然是黑色
//如果左右节点为null，null也是黑色
if (isBlack(sibling.left) && isBlack(sibling.right)) {
//兄弟节点没有一个红色子节点，父节点要向下跟兄弟节点合并
boolean parentBlack = isBlack(parent); //处理之前先检查下父节点是不是黑色
black(parent);
red(sibling);
if (parentBlack) {
//只需把 parent 当做被删除的节点处理即可
fixAfterRemove(parent);
}
} else { //兄弟节点至少有1个红色子节点，向兄弟节点借元素
//兄弟节点的左边是黑色，要对兄弟节点进行左旋转
if (isBlack(sibling.left)) {
rotateLeft(sibling);
sibling = parent.left; //兄弟节点要重新赋值
}
//sibling继承parent的颜色
color(sibling, colorOf(parent));
black(sibling.left);
black(parent);
rotateRight(parent);
}
}
}
/**
* 左旋
*
* @param grand
*/
private void rotateLeft(Node<K, V> grand) {
Node<K, V> parent = grand.right;
Node<K, V> child = parent.left;
grand.right = child;
parent.left = grand;
afterRotate(grand, parent, child);
}
/**
* 右旋
*
* @param grand
*/
private void rotateRight(Node<K, V> grand) {
Node<K, V> parent = grand.left;
Node<K, V> child = parent.right;
grand.left = child;
parent.right = grand;
afterRotate(grand, parent, child);
}
/**
* 公共代码：不管是左旋转、右旋转，都要执行
*
* @param grand 失衡节点
* @param parent
* @param child
*/
private void afterRotate(Node<K, V> grand, Node<K, V> parent, Node<K, V> child) {
//让parent成为子树的根节点
parent.parent = grand.parent;
if (grand.isLeftChild()) {
grand.parent.left = parent;
} else if (grand.isRightChild()) {
grand.parent.right = parent;
} else { //grand是根节点
table[index(grand)] = parent;
}
//更新child的parent
if (child != null) {
child.parent = grand;
}
//更新grand的parent
grand.parent = parent;
}
/**
* 给节点染色
*
* @param node
* @param color
* @return
*/
private Node<K, V> color(Node<K, V> node, boolean color) {
if (node == null) {
return node;
}
node.color = color;
return node;
}
/**
* 把节点染成红色
*
* @param node
* @return
*/
private Node<K, V> red(Node<K, V> node) {
return color(node, RED);
}
/**
* 把节点染成黑色
*
* @param node
* @return
*/
private Node<K, V> black(Node<K, V> node) {
return color(node, BLACK);
}
/**
* 判断当前节点是什么颜色的
* 空节点默认是黑色
*
* @param node
* @return
*/
private boolean colorOf(Node<K, V> node) {
return node == null ? BLACK : node.color;
}
/**
* 当前节点是否为黑色
*
* @param node
* @return
*/
private boolean isBlack(Node<K, V> node) {
return colorOf(node) == BLACK;
}
/**
* 当前节点是否为红色
*
* @param node
* @return
*/
private boolean isRed(Node<K, V> node) {
return colorOf(node) == RED;
}
private static class Node<K, V> {
int hash;
K key;
V value;
boolean color;
Node<K, V> left; //左子节点
Node<K, V> right; //右子节点
Node<K, V> parent; //父节点
public Node(K key, V value, Node<K, V> parent) {
this.key = key;
int hash = key == null ? 0 : key.hashCode();
this.hash = hash ^ (hash >>> 16);
this.value = value;
this.parent = parent;
}
//判断当前节点是不是叶子节点
public boolean isLeaf() {
return left == null && right == null;
}
//判断当前节点是不是拥有两个子节点
public boolean hasTwoChildren() {
return left != null && right != null;
}
//判断当前节点是不是左子树
public boolean isLeftChild() {
return parent != null && this == parent.left;
}
//判断当前节点是不是右子树
public boolean isRightChild() {
return parent != null && this == parent.right;
}
//返回兄弟结点
public Node<K, V> sibling() {
if (isLeftChild()) {
return parent.right;
}
if (isRightChild()) {
return parent.left;
}
return null;
}
@Override
public String toString() {
return "Node_" + key + "_" + value;
}
}
}
HashMap 升级为 LinkedHashMap
- 在 HashMap 的基础上维护元素的添加顺序，使得遍历的结果遵从添加顺序
package cn.xx.java.map;
import java.util.Objects;
/**
* @author xiexu
* @create 2021-08-19 4:30 下午
*/
public class LinkedHashMap<K, V> extends HashMap<K, V> {
private LinkedNode<K, V> first;
private LinkedNode<K, V> last;
@Override
public void clear() {
super.clear();
first = null;
last = null;
}
@Override
public boolean containsValue(V value) {
LinkedNode<K, V> node = first;
while (node != null) {
if (Objects.equals(value, node.value)) {
return true;
}
}
return false;
}
@Override
public void traversal(Visitor<K, V> visitor) {
if (visitor == null) {
return;
}
LinkedNode<K, V> node = first;
while (node != null) {
if (visitor.visit(node.key, node.value)) {
return;
}
node = node.next;
}
}
@Override
protected void afterRemove(Node<K, V> willNode, Node<K, V> removeNode) {
LinkedNode<K, V> linkedWillNode = (LinkedNode<K, V>) willNode;
LinkedNode<K, V> linkedRemovedNode = (LinkedNode<K, V>) removeNode;
if (linkedWillNode != linkedRemovedNode) {
//交换linkedWillNode和linkedRemovedNode在链表中的位置
//交换prev
LinkedNode<K, V> tmp = linkedWillNode.prev;
linkedWillNode.prev = linkedRemovedNode.prev;
linkedRemovedNode.prev = tmp;
if (linkedWillNode.prev == null) {
first = linkedWillNode;
} else {
linkedWillNode.prev.next = linkedWillNode;
}
if (linkedRemovedNode.prev == null) {
first = linkedRemovedNode;
} else {
linkedRemovedNode.prev.next = linkedRemovedNode;
}
//交换next
tmp = linkedWillNode.next;
linkedWillNode.next = linkedRemovedNode.next;
linkedRemovedNode.next = tmp;
if (linkedWillNode.next == null) {
last = linkedWillNode;
} else {
linkedWillNode.next.prev = linkedWillNode;
}
if (linkedRemovedNode.next == null) {
last = linkedRemovedNode;
} else {
linkedRemovedNode.next.prev = linkedRemovedNode;
}
}
LinkedNode<K, V> prev = linkedRemovedNode.prev;
LinkedNode<K, V> next = linkedRemovedNode.next;
if (prev == null) {
first = next;
} else {
prev.next = next;
}
if (next == null) {
last = prev;
} else {
next.prev = prev;
}
}
protected Node<K, V> createNode(K key, V value, Node<K, V> parent) {
LinkedNode node = new LinkedNode(key, value, parent);
if (first == null) {
first = last = node;
} else {
last.next = node;
node.prev = last;
last = node;
}
return node;
}
private static class LinkedNode<K, V> extends Node<K, V> {
LinkedNode<K, V> prev;
LinkedNode<K, V> next;
public LinkedNode(K key, V value, Node<K, V> parent) {
super(key, value, parent);
}
}
}
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