P519set接口实现类HashSet
public class HashSetStructure {
public static void main(String[] args) {
//模拟一个HashSet的底层(HashMap的底层)
//1.创建1个数组,数组的类型是Node[]
//2.有些人直接把Node数组成为表
Node[] table =new Node[16];
System.out.println("table="+table);
//3.创建结点
Node john = new Node("john2",null);
table[2]=john;
Node jack=new Node("jack3",null);
john.next=jack;//将jack挂点挂载到john
Node rose = new Node("Rose4", null);
Node lucy = new Node("lucy5", null);
table[3]=lucy;//把lucy放到table表的索引
jack.next=rose;//将rose结点挂载到jack
System.out.println("table="+table);
}
}
class Node {//结点存储数据,可以指向下一个,从而形成链表
Object item;//存放数据
Node next;//指向下一个结点
public Node(Object item, Node next) {
this.item = item;
this.next = next;
}
}
P520HashSet扩容机制
P521HashSet源码解读
public class HashSetSource {
public static void main(String[] args) {
HashSet hashSet = new HashSet();
hashSet.add("java");//到此位置,第1 次add 分析完毕.
hashSet.add("php");//到此位置,第2 次add 分析完毕
hashSet.add("java");
System.out.println("set=" + hashSet);//输出set=[java, php]
/*
对HashSet的解读数码解读
1. 执行HashSet()
public HashSet() {
map = new HashMap<>();
}
2. 执行add()
public boolean add(E e) {//e = "java"
return map.put(e, PRESENT)==null;//(static) PRESENT = new Object();
}
3.执行put() , 该方法会执行hash(key) 得到key对应的hash值,算法h = key.hashCode()) ^ (h >>> 16)
public V put(K key, V value) {//key = "java" value = PRESENT 共享
return putVal(hash(key), key, value, false, true);
}
4.执行putVal
final V putVal(int hash, K key, V value, boolean onlyIfAbsent,
boolean evict) {
Node<K,V>[] tab; Node<K,V> p; int n, i; //定义了辅助变量
//table 就是HashMap 的一个数组,类型是Node[]
//if 语句表示如果当前table 是null, 或者大小=0
//就是第一次扩容,到16 个空间.
if ((tab = table) == null || (n = tab.length) == 0)
n = (tab = resize()).length;
//(1)根据key,得到hash 去计算该key 应该存放到table 表的哪个索引位置
//并把这个位置的对象,赋给p
//(2)判断p 是否为null
//(2.1) 如果p 为null, 表示还没有存放元素, 就创建一个Node (key="java",value=PRESENT)
//(2.2) 就放在该位置tab[i] = newNode(hash, key, value, null)
if ((p = tab[i = (n - 1) & hash]) == null)
tab[i] = newNode(hash, key, value, null);
else {
//追第二次add部分
//一个开发技巧提示: 在需要局部变量(辅助变量)时候,在创建
Node<K,V> e; K k; //
//如果当前索引位置对应的链表的第一个元素和准备添加的key 的hash 值一样
//并且满足下面两个条件之一:
//(1) 准备加入的key 和p 指向的Node 结点的key 是同一个对象
//(2) p 指向的Node 结点的key 的equals() 和准备加入的key 比较后相同
//就不能加入
if (p.hash == hash &&
((k = p.key) == key || (key != null && key.equals(k))))//判断对象、内容相同
e = p;
//再判断p 是不是一颗红黑树,
//如果是一颗红黑树,就调用putTreeVal , 来进行添加
else if (p instanceof TreeNode)
e = ((TreeNode<K,V>)p).putTreeVal(this, tab, hash, key, value);
else {//如果table 对应索引位置,已经是一个链表, 就使用for 循环比较
//(1) 依次和该链表的每一个元素比较后,都不相同, 则加入到该链表的最后
// 注意在把元素添加到链表后,立即判断该链表是否已经达到8 个结点
// , 就调用treeifyBin() 对当前这个链表进行树化(转成红黑树)
// 注意,在转成红黑树时,要进行判断, 判断条件
// if (tab == null || (n = tab.length) < MIN_TREEIFY_CAPACITY(64))
// resize();
// 如果上面条件成立,先table 扩容.
// 只有上面条件不成立时,才进行转成红黑树
//(2) 依次和该链表的每一个元素比较过程中,如果有相同情况,就直接break
for (int binCount = 0; ; ++binCount) {
if ((e = p.next) == null) {
p.next = newNode(hash, key, value, null);
if (binCount >= TREEIFY_THRESHOLD(8) - 1) // -1 for 1st
treeifyBin(tab, hash);
break;
}
if (e.hash == hash &&
((k = e.key) == key || (key != null && key.equals(k))))
break;
p = e;
}
}
if (e != null) { // existing mapping for key
V oldValue = e.value;
if (!onlyIfAbsent || oldValue == null)
e.value = value;
afterNodeAccess(e);
return oldValue;
}
}
++modCount;
//size 就是我们每加入一个结点Node(k,v,h,next), size++
if (++size > threshold)
resize();//扩容
afterNodeInsertion(evict);
return null;
}
*/
}
}
P523JavaSet底层机制说明,分析HashSet的扩容和转成红黑树机制
public class HashSetSource {
public static void main(String[] args) {
/*
HashSet 底层是HashMap, 第一次添加时,table 数组扩容到16,
临界值(threshold)是16*加载因子(loadFactor)是0.75 = 12
如果table 数组使用到了临界值12,就会扩容到16 * 2 = 32,
新的临界值就是32*0.75 = 24, 依次类推
*/
HashSet hashSet = new HashSet();
/*
for (int i = 0; i < 100; i++) {
hashSet.add(i);
}
在Java8 中, 如果一条链表的元素个数到达TREEIFY_THRESHOLD(默认是8 ),
并且table 的大小>= MIN_TREEIFY_CAPACITY(默认64),就会进行树化(红黑树),
否则仍然采用数组扩容机制
*/
for (int i = 1; i <=7 ; i++) {//在table 的某一条链表上添加了7 个A 对象
hashSet.add(new A(i));
}
/*
当我们向hashset 增加一个元素,-> Node -> 加入table , 就算是增加了一个size++
*/
for (int i = 1; i <=7 ; i++) {//在table 的另一条链表上添加了7 个B 对象
hashSet.add(new B(i));
}
System.out.println(hashSet);
}
}
class B{
private int n;
public B(int n) {
this.n = n;
}
@Override
public int hashCode(){
return 50;
}
}
class A{
private int n;
public A(int n) {
this.n = n;
}
@Override
public int hashCode(){
return 100;
}
}
P525set接口实现类
public class HashSetE1 {
public static void main(String[] args) {
HashSet hashSet = new HashSet();
hashSet.add(new E("y1",1));
hashSet.add(new E("y2",2));
hashSet.add(new E("y1",1));
System.out.println(hashSet);
}
}
class E{
private String name;
private int age;
public E(String name, int age) {
this.name = name;
this.age = age;
}
@Override
public String toString() {
return "E{" +
"name='" + name + '\'' +
", age=" + age +
'}';
}
@Override
public boolean equals(Object o) {//如果name 和age 值相同,则返回相同的equals
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
E e = (E) o;
return age == e.age &&
Objects.equals(name, e.name);
}
@Override
public int hashCode() //如果name 和age 值相同,则返回相同的hash 值
return Objects.hash(name, age);
}
}
public class HSE2 {
public static void main(String[] args) {
HashSet hashSet = new HashSet();
hashSet.add(new Em("y1",111,new MyDate(21,1,1)));
hashSet.add(new Em("y1",111,new MyDate(21,2,1)));
hashSet.add(new Em("y1",111,new MyDate(21,1,1)));
System.out.println(hashSet);
}
}
class Em{
private String name;
private double sal;
private MyDate birthday;
public Em(String name, double sal, MyDate birthday) {
this.name = name;
this.sal = sal;
this.birthday = birthday;
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
Em em = (Em) o;
return Objects.equals(name, em.name) &&
Objects.equals(birthday, em.birthday);
}
@Override
public int hashCode() {
return Objects.hash(name, birthday);
}
@Override
public String toString() {
return "Em{" +
"name='" + name + '\'' +
", sal=" + sal +
", birthday=" + birthday +
'}';
}
}
class MyDate{
private int year;
private int moth;
private int day;
public MyDate(int year, int moth, int day) {
this.year = year;
this.moth = moth;
this.day = day;
}
@Override
public String toString() {
return "MyDate{" +
"year=" + year +
", moth=" + moth +
", day=" + day +
'}';
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
MyDate myDate = (MyDate) o;
return year == myDate.year &&
moth == myDate.moth &&
day == myDate.day;
}
@Override
public int hashCode() {
return Objects.hash(year, moth, day);
}
}
P527LinkedHashSet
public class LinkedHashSetSource {
public static void main(String[] args) {
Set set = new LinkedHashSet();
set.add(new String("A"));
set.add(456);
set.add(456);
set.add(new Customer("liu",1001));
set.add(123);
set.add("HSP");
System.out.println(set);//输出[A, 456, New.Customer@10f87f48, 123, HSP]
//1.linkedHHashSet加入顺序和取出元素的顺序
//2.linkedHHashSet底层维护的是一个linkedHHashMap(是HashMap的子类)
//3.LinkedHashSet底层结构i(数组table和双向链表)
//4.添加第一次的时候,直接将数组Table扩容到16,存放的结点类型是LinkedHashMap$Entry
//5.数组是HashMap$Node[]存放的元素/数据是LinkedHashMap$Entry类型
}
}
class Customer{
private String name;
private int no;
public Customer(String name, int no) {
this.name = name;
this.no = no;
}
}
P529set接口实现类
public class LinkedHashSetE {
public static void main(String[] args) {
LinkedHashSet lkht = new LinkedHashSet();
lkht.add(new Car("1a",1));
lkht.add(new Car("1B",2));
lkht.add(new Car("1c",3));
lkht.add(new Car("1d",4));
lkht.add(new Car("1c",5));
lkht.add(new Car("1B",2));
System.out.println(lkht);
}
}
class Car{
private String name;
private double price;
public Car(String name, double price) {
this.name = name;
this.price = price;
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
Car car = (Car) o;
return Double.compare(car.price, price) == 0 &&
Objects.equals(name, car.name);
}
@Override
public int hashCode() {
return Objects.hash(name, price);
}
@Override
public String toString() {
return "\nCar{" +
"name='" + name + '\'' +
", price=" + price +
'}';
}
}
P530Map接口的特点
public class Map_ {
public static void main(String[] args) {
//老韩解读Map 接口实现类的特点, 使用实现类HashMap
// 1. Map 与Collection 并列存在。用于保存具有映射关系的数据:Key-Value(双列元素)
// 2. Map 中的key 和value 可以是任何引用类型的数据,会封装到HashMap$Node 对象中
// 3. Map 中的key 不允许重复,原因和HashSet 一样,前面分析过源码.
// 4. Map 中的value 可以重复
// 5. Map 的key 可以为null, value 也可以为null ,
// 注意key 为null,只能有一个,value 为null ,可以多个
//6. 常用String 类作为Map 的key
//7. key 和value 之间存在单向一对一关系,即通过指定的key 总能找到对应的value
Map map = new HashMap();
map.put("n1","1y");
map.put("n2","2y");
map.put("n1","3y");//输入{n1=3y, n2=2y},当有相同的K,就相当于替换
map.put("n3","3y");//输出{n1=3y, n2=2y, n3=3y}
//3.4.5
map.put(null,null);//{null=null, n1=3y, n2=2y, n3=3y}
map.put(null,"abc");//{null=abc, n1=3y, n2=2y, n3=3y},替换
map.put("n4",null);//{null=abc, n1=3y, n2=2y, n3=3y, n4=null}
//6
map.put(1,"m1");//{null=abc, 1=m1, n1=3y, n2=2y, n3=3y, n4=null}
System.out.println(map);//输出{n1=1y, n2=2y}
//7. 通过get 方法,传入key ,会返回对应的value
System.out.println(map.get("n1"));//输出3y
}
}
P531Map接口的特点2
public class MapSource {
public static void main(String[] args) {
Map map = new HashMap();
map.put("no1", "韩顺平");//k-v
map.put("no2", "张无忌");//k-v
//1.k-v最后是HashMap$Node node=newNode(hash,key,value,null)
//2.k-v为了程序员的遍历,还会创建EntrySet集合,该集合存放的元素的类型是Entry
//而一个Entry对象就有k,v EntrySet<Entry<k,v>,
// 即为transient Set<Map.Entry<K,V>> entrySet;
//3.entrySet中,定义类型是Map.Entry,但是实际上存放的还是HashMap$Node
//这个是因为HashMap$Node implement Map.Entry
//4.当把HashMap$Node 对象存放到entrySet就方便我们遍历,因为Map.entry提供了重要的方法
//一个是getValue,一个是getkey();
Set set=map.entrySet();
System.out.println(set.getClass());//输出class java.util.HashMap$EntrySe
for (Object oBJ :set) {
System.out.println(oBJ.getClass());
//输出class java.util.HashMap$Node class java.util.HashMap$Node
//为了从 HashMap$Node中取出K-V
//先进行一个向下转型
Map.Entry entry=(Map.Entry) oBJ;
System.out.println(entry.getKey()+"\t"+entry.getValue());
//输出 no2 张无忌 no1 韩顺平
}
Set set1=map.keySet();
System.out.println(set1.getClass());
Collection values = map.values();
System.out.println(values.getClass());
//输出class java.util.HashMap$KeySet,
// class java.util.HashMap$Value
}
}
P532Map接口方法
public class MapMethod {
public static void main(String[] args) {
//演示map 接口常用方法
//1.添加
Map map = new HashMap();
map.put("邓超", new Book("",100));//OK
map.put("邓超", "孙俪");//替换-> 一会分析源码
map.put("王宝强", "马蓉");//OK
map.put("宋喆", "马蓉");//OK
map.put("刘令博", null);//OK
map.put(null, "刘亦菲");//OK
map.put("gj", "gjl");//OK
map.put("hsp", "hsp 的老婆");
System.out.println("map=" + map);
// remove:根据键删除映射关系
map.remove(null);
System.out.println("map=" + map);//此时输出null=刘亦菲没有了
// get:根据键获取值
Object val = map.get("gj");
System.out.println("val=" + val);//输出val=gjl
// size:获取元素个数
System.out.println("k-v=" + map.size());//目前有6个
// isEmpty:判断个数是否为0
System.out.println(map.isEmpty());//F
// clear:清除k-v
// map.clear();
System.out.println("map=" + map);//输出{}
// containsKey:查找键是否存在
System.out.println("结果=" + map.containsKey("hsp"));//T
}
}
class Book{
private String name;
private int num;
public Book(String name, int num) {
this.name = name;
this.num = num;
}
}
P533Map的六种遍历方式
public class MapMethod {
public static void main(String[] args) {
Map map = new HashMap();
map.put("邓超", "1孙俪");//替换-> 一会分析源码
map.put("王宝强", "2马蓉");//OK
map.put("宋喆", "3马蓉");//OK
map.put("刘令博", null);//OK
map.put(null, "5刘亦菲");//OK
map.put("gj", "6gjl");//OK
map.put("hsp", "7hsp 的老婆");
System.out.println("map=" + map);
//第一组: 先取出所有的Key , 通过Key 取出对应的Value
Set keySet = map.keySet();
Iterator iterator = keySet.iterator();
while (iterator.hasNext()) {
Object next = iterator.next();
System.out.println(map.get(next));
}
for (Object key :keySet) {
System.out.println(map.get(key));
//输出1孙俪//3马蓉//null//5刘亦菲//6gjl//7hsp 的老婆
}
//第二组取出所有的values
Collection values = map.values();
//这里可以使用所有的collection遍历方式,增强for,iterator,
//第三组通过entrySet来取出k-v,将Node做成Entry放入Set中
Set entrySet = map.entrySet();
for (Object entry :entrySet) {
//将entry转成Map.Entry
Map.Entry m = (Map.Entry) entry;
//m提供了两个方法,getkey和getvalue
System.out.println(m.getKey()+"-"+m.getValue());
//输出邓超-1孙俪//宋喆-3马蓉//刘令博-null//null-5刘亦菲
// gj-6gjl//hsp-7hsp 的老婆//王宝强-2马蓉
}
//迭代器
Iterator iterator3 = entrySet.iterator();
while (iterator3.hasNext()) {
Object entry = iterator3.next();
//System.out.println(next.getClass());
// HashMap$Node -实现-> Map.Entry (getKey,getValue)
// 向下转型Map.Entry
Map.Entry m = (Map.Entry) entry;
System.out.println(m.getKey() + "-" + m.getValue());
}
}
}
P535课堂练习
public class MapE1 {
public static void main(String[] args) {
Map hashMap = new HashMap();
hashMap.put(1,new EM(1,111));
hashMap.put(2,new EM(2,112));
hashMap.put(3,new EM(3,113));
for (Object key : hashMap.keySet()) {
EM em = (EM) hashMap.get(key);
if(em.getSal()>112) {
System.out.println(em);
//EM{id=3, sal=113.0}
}
}
//迭代器
Set entryset = hashMap.entrySet();
Iterator iterator = entryset.iterator();
while (iterator.hasNext()) {
//Object next = iterator.next();//拿出的是Mapentry
Map.Entry entry = (Map.Entry) iterator.next();
//entry的运行类型是hashmap$Node
//通过entry取得getkey和getvalue\
EM em1 = (EM) entry.getValue();
if (em1.getSal() > 112) {
System.out.println(em1);
//EM{id=3, sal=113.0}
}
}
}
}
class EM{
private int id;
private double sal;
public EM(int id, double sal) {
this.id = id;
this.sal = sal;
}
@Override
public String toString() {
return "EM{" +
"id=" + id +
", sal=" + sal +
'}';
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public double getSal() {
return sal;
}
public void setSal(double sal) {
this.sal = sal;
}
}
P536HMap底层机构
P537HMap的底层机制及源码剖析
public class HashMapSource1 {
public static void main(String[] args) {
HashMap map = new HashMap<>();
map.put("java", 10);//ok
map.put("php", 10);//ok
map.put("java", 20);//替换value,此时
System.out.println("map=" + map);//
/*老韩解读HashMap 的源码+图解
1. 执行构造器new HashMap()
初始化加载因子loadfactor = 0.75
HashMap$Node[] table = null
2. 执行put 调用hash 方法,计算key 的hash 值(h = key.hashCode()) ^ (h >>> 16)
public V put(K key, V value) {//K = "java" value = 10
// return putVal(hash(key), key, value, false, true);
3.执行putVal
源码如下:
final V putVal(int hash, K key, V value, boolean onlyIfAbsent,
boolean evict) {
Node<K,V>[] tab; Node<K,V> p; int n, i;//辅助变量
//如果底层的table 数组为null, 或者length =0 , 就扩容到16
if ((tab = table) == null || (n = tab.length) == 0)
n = (tab = resize()).length;//此时table为16,全为null
//取出hash 值对应的table 的索引位置的Node, 如果为null, 就直接把加入的k-v
//, 创建成一个Node ,加入该位置即可
if ((p = tab[i = (n - 1) & hash]) == null)//根据hash确定索引位置有无元素,若无
tab[i] = newNode(hash, key, value, null);
//执行完此句之后,table有一个元素,
else {
Node<K,V> e; K k;//辅助变量
// 如果table 的索引位置的key 的hash 相同和新的key 的hash 值相同,
// 并满足(table 现有的结点的key 和准备添加的key 是同一个对象|| equals 返回真)
// 就认为不能加入新的k-v
if (p.hash == hash &&
((k = p.key) == key || (key != null && key.equals(k))))
e = p;
else if (p instanceof TreeNode)//如果当前的table 的已有的Node 是红黑树,就按照红黑树的方式处
e = ((TreeNode<K,V>)p).putTreeVal(this, tab, hash, key, value);
else {//这个后面就是链表
//如果找到的结点,后面是链表,就循环比较
for (int binCount = 0; ; ++binCount) {//死循环
if ((e = p.next) == null) {//如果整个链表,没有和他相同,就加到该链表的最后
//加入后,判断当前链表的个数,是否已经到8 个,到8 个,后
p.next = newNode(hash, key, value, null);
if (binCount >= TREEIFY_THRESHOLD - 1) // -1 for 1st
//T-T=8
treeifyBin(tab, hash);//就调用treeifyBin 方法进行红黑树的转换
break;
}
if (e.hash == hash &&
((k = e.key) == key || (key != null && key.equals(k))))
break;//如果在循环比较过程中,发现有相同,就break,就只是替换value
p = e;
}
}
if (e != null) { // existing mapping for key
V oldValue = e.value;
if (!onlyIfAbsent || oldValue == null)
e.value = value;//值已经被替换了
afterNodeAccess(e);
return oldValue;
}
}
++modCount;//每增加一个Node ,就size++
if (++size > threshold)//threshold=12,其实到达12就扩容,12是第一次,其实是临界值
resize();
afterNodeInsertion(evict);
return null;
}
源码:resize()
final Node<K,V>[] resize() {
Node<K,V>[] oldTab = table;
int oldCap = (oldTab == null) ? 0 : oldTab.length;
int oldThr = threshold;
int newCap, newThr = 0;
if (oldCap > 0) {
if (oldCap >= MAXIMUM_CAPACITY) {
threshold = Integer.MAX_VALUE;
return oldTab;
}
else if ((newCap = oldCap << 1) < MAXIMUM_CAPACITY &&
oldCap >= DEFAULT_INITIAL_CAPACITY)
newThr = oldThr << 1; // double threshold
}
else if (oldThr > 0) // initial capacity was placed in threshold
newCap = oldThr;
else { // zero initial threshold signifies using defaults
newCap = DEFAULT_INITIAL_CAPACITY;//实际上D-I-C=16,D-L-I=0.75
newThr = (int)(DEFAULT_LOAD_FACTOR * DEFAULT_INITIAL_CAPACITY);
}
if (newThr == 0) {
float ft = (float)newCap * loadFactor;
newThr = (newCap < MAXIMUM_CAPACITY && ft < (float)MAXIMUM_CAPACITY ?
(int)ft : Integer.MAX_VALUE);
}
threshold = newThr;
@SuppressWarnings({"rawtypes","unchecked"})
Node<K,V>[] newTab = (Node<K,V>[])new Node[newCap];
table = newTab;
if (oldTab != null) {
for (int j = 0; j < oldCap; ++j) {
Node<K,V> e;
if ((e = oldTab[j]) != null) {
oldTab[j] = null;
if (e.next == null)
newTab[e.hash & (newCap - 1)] = e;
else if (e instanceof TreeNode)
((TreeNode<K,V>)e).split(this, newTab, j, oldCap);
else { // preserve order
Node<K,V> loHead = null, loTail = null;
Node<K,V> hiHead = null, hiTail = null;
Node<K,V> next;
do {
next = e.next;
if ((e.hash & oldCap) == 0) {
if (loTail == null)
loHead = e;
else
loTail.next = e;
loTail = e;
}
else {
if (hiTail == null)
hiHead = e;
else
hiTail.next = e;
hiTail = e;
}
} while ((e = next) != null);
if (loTail != null) {
loTail.next = null;
newTab[j] = loHead;
}
if (hiTail != null) {
hiTail.next = null;
newTab[j + oldCap] = hiHead;
}
}
}
}
}
return newTab;
}
源码:treeifyBin
5. 关于树化(转成红黑树)
//如果table 为null ,或者大小还没有到64,暂时不树化,而是进行扩容.
//否则才会真正的树化-> 剪枝
final void treeifyBin(Node<K,V>[] tab, int hash) {
int n, index; Node<K,V> e;
if (tab == null || (n = tab.length) < MIN_TREEIFY_CAPACITY)//注意M_T_C=64
resize();
else if ((e = tab[index = (n - 1) & hash]) != null) {
TreeNode<K,V> hd = null, tl = null;
do {
TreeNode<K,V> p = replacementTreeNode(e, null);
if (tl == null)
hd = p;
else {
p.prev = tl;
tl.next = p;
}
tl = p;
} while ((e = e.next) != null);
if ((tab[index] = hd) != null)
hd.treeify(tab);
}
}
*/
}
}
P538HMap扩容树化触发
public class HashMapSource2 {
public static void main(String[] args) {
HashMap hashMap = new HashMap();
for (int i = 1; i <=12; i++) {
hashMap.put(new A(i),"hello");
}
hashMap.put("aaa","bb");
//当8的时候不树话,9扩容32,10的时候扩容64,加入11进行treeNode
System.out.println(hashMap);
//布置一个任务,自己设计代码去验证,table 的扩容
// 0 -> 16(12) -> 32(24) -> 64(64*0.75=48)-> 128 (96) ->
// 自己设计程序,验证-》增强自己阅读源码能力. 看别人代码.
}
}
class A{
private int num;
public A(int num) {
this.num = num;
}
@Override//所以对象的hashcode都一样
public int hashCode() {
return 100;
}
@Override
public String toString() {
return "\nA{" +
"num=" + num +
'}';
}
}