笔记：
var1 == var2 ?
-------------------------
stu.getClass() == Student.class ? //精准判断 Class clazz = Student.class
stu instanceof Student ? //不是精准判断。
Class clazz = List.class ;
Class clazz2= ... ;
clazz2 == clazz ?
xxx.getClass() ;
成员变量 === 属性 === 字段 === Field
成员函数 === 方法 === Method
构造函数 === 构造器 === 构造子 === Constructor
类 === Class
TreeSet
---------------
1.使用比较方法判断对象是否重复。
2.比较方法实现有两种
a)自定义Comparator比较器，和TreeSet关联。
b)让javaBean实现Comparable接口，实现CompareTo()方法。
3.TreeSet可以容纳null元素。
4.TreeSet可以使用降序排列。
通过descendingIterator()方法得到降序迭代器实现。
5.TreeSet默认升序排列。
HashMap 1 key-value 键值对
2 Entey 每一对Key和value
3 每一个key存在keySet中通过map.keySet()获取
4 遍历有两种方式：
KeySet遍历 通过Map.get(Object key)获取value的值
EnetySet遍历 通过map.entrySet()获取Entey的Set集合后 循环遍历Entey的key或value
效率上来说HashMap 比HashSet更快 因为是使用唯一的键来获取对象
作业：
1.定义罪犯Criminal类，height(身高)/weight(体重)/blood(血型)/home(籍贯)属性。
重写hashcode和equals，使用四个属性的组合进行实现。 创建HashSet集合，里面存放20个Criminal对 象，其中O型血2人，A型血3人，B型血4人，AB型血1人，其余血型不详。
注意:hashcode()方法实现时，要求身高、体重、和血型三个属性合成一个数字， 实现两两比较的高效 算法
代码：
package com.work.eleven;
import com.work.eleven.*;
public class Criminal implements Comparable{
private int height;
private int weight;
private int blood;
private String home;
public int getHeight() {
return height;
}
public void setHeight(int height) {
this.height = height;
}
public int getWeight() {
return weight;
}
public void setWeight(int weight) {
this.weight = weight;
}
public int getBlood() {
return blood;
}
public void setBlood(int blood) {
this.blood = blood;
}
public String getHome() {
return home;
}
public void setHome(String home) {
this.home = home;
}
public Criminal(int height, int weight, String bloods,String home) {
String blood1=bloods.toLowerCase();
if (height <= 0) {
System.out.println("身高需为正数 ");
System.exit(-1);
} else if (weight <= 0) {
System.out.println("体重需为正数 ");
System.exit(-1);
}
else if (!blood1.equals("a")&&!blood1.equals("b")&&!blood1.equals("ab")&&!blood1.equals("o")&&!blood1.equals("")) {
System.out.println("血型错误 ");
System.exit(-1);
} else {
this.height=height;
this.weight=weight;
if(blood1.equals("")) this.blood=0;
if(blood1.equals("a")) this.blood=1;
if(blood1.equals("b")) this.blood=2;
if(blood1.equals("ab")) this.blood=3;
if(blood1.equals("o")) this.blood=4;
this.home= home;
}
}
@Override
public int compareTo(Object obj) {
if(obj==null) return 1;
else{
if(obj instanceof Criminal){
Criminal criminal=(Criminal)obj;
//比较身高
int heightResult = this.height-criminal.height;
// 身高不一样
if(heightResult!=0) return heightResult;
else {
//比较体重
int weightResult = this.weight-criminal.weight;
// 体重不一样
if(weightResult!=0) return weightResult;
else{
//比较血型
int bloodResult = this.blood-criminal.blood;
// 血型不一样
if(bloodResult!=0) {
return bloodResult;
}
else{
return this.home.compareTo(criminal.home);
}
}
}
}
return 0;
}
}
/**
* 重写hashcode方法
*/
@Override
public int hashCode() {
int h0 = 0 << 32;
//身高左16位
int h1 = (ArrayTools.int2Bytes(height)[0] & 0xff) << 16;
/*System.out.println("h1= "+h1);*/
//体重左移8位
int h2 = (ArrayTools.int2Bytes(weight)[0] & 0xff) << 8;
/*System.out.println("h2= "+h2);*/
//血型位置不变
int h3 = (ArrayTools.int2Bytes(blood)[0] & 0xff) << 0;
/*System.out.println("h3= "+h3);*/
int identityResult = h0 | h1 | h2 | h3;
/*System.out.println("identityResult= "+identityResult);*/
return home == null ? identityResult : identityResult + home.hashCode();
}
}
package com.work.eleven;
public class ArrayTools {
/**
*
* 整数转换为字节数组 ；向右移位，然后强转截断。
*/
public static byte[] int2Bytes(int i) {
byte[] bytes = new byte[4];
bytes[0] = (byte) i;// 低位
/*System.out.println("bytes[0]= "+bytes[0]);*/
bytes[1] = (byte) (i >> 8);// 次低位
/*System.out.println("bytes[1]= "+bytes[1]);*/
bytes[2] = (byte) (i >> 16);// 次高位
/*System.out.println("bytes[2]= "+bytes[2]);*/
bytes[3] = (byte) (i >> 24); // 高位
/*System.out.println("bytes[3]= "+bytes[3]);*/
return bytes;
}
/**
*
* 字节数组 转 为整数 ，向左移位，由于向左移位，先转换为整数 ，缺的用符号位补齐，故用&0xFF去除
*/
/* public static int bytes2Int(byte[] bytes) {
int i0 = bytes[3] << 24;
int i1 = (bytes[2] & 0xFF) << 16;
int i2 = (bytes[1] & 0xFF) << 8;
int i3 = (bytes[0] & 0xFF) << 0;
return i0 | i1 | i2 | i3;
}*/
}
package com.work.eleven;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;
public class HashSetCriminal {
public static void main(String[] args) {
Set<Criminal> criminalset = new HashSet<Criminal>();
criminalset.add(new Criminal(175,165,"A","Beijing"));
criminalset.add(new Criminal(176,165,"A","Beijing"));
criminalset.add(new Criminal(177,166,"A","Beijing"));
criminalset.add(new Criminal(178,166,"O","Beijing"));
criminalset.add(new Criminal(179,167,"O","Beijing"));
criminalset.add(new Criminal(180,167,"B","Beijing"));
criminalset.add(new Criminal(181,168,"B","Beijing"));
criminalset.add(new Criminal(181,168,"B","Beijing"));
criminalset.add(new Criminal(181,169,"B","Beijing"));
criminalset.add(new Criminal(182,169,"AB","Beijing"));
criminalset.add(new Criminal(182,170,"","Beijing"));
criminalset.add(new Criminal(183,170,"","Beijing"));
criminalset.add(new Criminal(183,171,"","Beijing"));
criminalset.add(new Criminal(184,171,"","Beijing"));
criminalset.add(new Criminal(184,172,"","Beijing"));
criminalset.add(new Criminal(185,172,"","Beijing"));
criminalset.add(new Criminal(185,173,"","Beijing"));
criminalset.add(new Criminal(186,173,"",""));
criminalset.add(new Criminal(186,174,"",""));
criminalset.add(new Criminal(187,174,"",""));
System.out.println(criminalset.size());
for(Iterator<Criminal> it = criminalset.iterator() ; it.hasNext() ; ){
System.out.println(it.next());
}
}
}运行结果：
20
com.work.eleven.Criminal@5667d59e
com.work.eleven.Criminal@bbae00
com.work.eleven.Criminal@5666d49e
com.work.eleven.Criminal@5663d0a0
com.work.eleven.Criminal@5663d0a0
com.work.eleven.Criminal@baad00
com.work.eleven.Criminal@5664d1a1
com.work.eleven.Criminal@5661cfa2
com.work.eleven.Criminal@5664d29e
com.work.eleven.Criminal@565dcd9f
com.work.eleven.Criminal@5665d39e
com.work.eleven.Criminal@5660cea2
com.work.eleven.Criminal@baae00
com.work.eleven.Criminal@5663d1a0
com.work.eleven.Criminal@5667d49e
com.work.eleven.Criminal@565fce9f
com.work.eleven.Criminal@5665d29e
com.work.eleven.Criminal@5666d39e
com.work.eleven.Criminal@565ecd9f
com.work.eleven.Criminal@5662cfa0
作业2：
key(键) - value(值) :kv对.
创建HashMap，Person为key，Dog为value。
存放100元素，遍历map集合，两种方式。EntrySet + KeySet.
删除操作。remove();
代码：
package com.work.eleven;
/**
*
*/
public class Dog implements Comparable{
private String color = "" ;
private int weight ;
private String category = "";
public Dog(String color, int weight, String category) {
if(color == null)
throw new NullPointerException("color不能为空！");
if(category == null)
throw new NullPointerException("category不能为空！");
this.color = color;
this.weight = weight;
this.category = category;
}
public String getColor() {
return color;
}
public void setColor(String color) {
if(color == null)
throw new NullPointerException("color不能为空！");
this.color = color;
}
public int getWeight() {
return weight;
}
public void setWeight(int weight) {
this.weight = weight;
}
public String getCategory() {
return category;
}
public void setCategory(String category) {
if(category == null)
throw new NullPointerException("category不能为空！");
this.category = category;
}
public int compareTo(Object o){
if(o == null){
return 1 ;
}
//
if(o instanceof Dog){
Dog dog = (Dog)o ;
int catResult = this.category.compareTo(dog.category);
//比较品种
if(catResult != 0){
return catResult ;
}
//品种相同
else{
//比较
int colRes = this.color.compareTo(dog.color);
//颜色 不同
if(colRes != 0){
return colRes ;
}
//颜色相同
else{
//比较体重
return this.weight - dog.weight ;
}
}
}
return -1 ;
}
/**
* 重写toString方法()
*/
public String toString() {
return "category= "+category+" color= "+color+" weight= "+weight + " Dog.hascode= "+hashCode();
}
}
package com.work.eleven;
/**
* hashcode + equlas
*/
public class Person {
private String name;
private int age;
public Person(String name, int age) {
super();
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
//
public int hashCode() {
return name == null ?age : name.hashCode() + age ;
}
public String toString() {
return "name= "+name+" age= "+age+" Person.hascode= "+hashCode();
}
public boolean equals(Object obj) {
if(obj == null)
return false ;
if(obj == this)
return true ;
//精准判断
if(obj.getClass() == Person.class){
Person p = (Person)obj;
//name是否相同
boolean nameEqu = false ;
if(this.name == null){
if(p.name == null){
nameEqu =true ;
}
else{
nameEqu = false ;
}
}
//name 不null
else{
nameEqu = name.equals(p.name);
}
//age 是否相同
boolean ageEqu = (this.age == p.age) ;
//
return nameEqu && ageEqu ;
}
return false ;
}
}
package com.work.eleven;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
public class PerDogMap {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Map<Person, Dog> pdmap=new HashMap<Person, Dog>();
for (int i=1;i<101;i++){
pdmap.put(new Person("Bruce"+i,i+10), new Dog("color"+i, i+10,"category"+i));
}
System.out.println("===============================================keySet遍历=====================================================");
//KeySet遍历
Set<Person> personKeySet=pdmap.keySet();
for(Person person : personKeySet){
System.out.println("Person : "+person.toString()+" and Dog : "+pdmap.get(person).toString());
}
System.out.println("===============================================EntrySet遍历=====================================================");
Set<Entry<Person, Dog>> personEnteySet=pdmap.entrySet();
for(Entry<Person,Dog> personEntey : personEnteySet){
System.out.println("Person : "+personEntey.getKey().toString()+" and Dog : "+personEntey.getValue().toString());
}
System.out.println("===============================================Remove=====================================================");
Iterator<Person> personiterator = pdmap.keySet().iterator();
Dog dog;
for(int j=90;j<101;j++){
dog= pdmap.remove(new Person("Bruce"+j,j+10));
System.out.println("删除了"+dog.toString());
}
}
}运行结果（部分）：
Person : name= Bruce62 age= 72 Person.hascode= 1820524139 and Dog : category= category62 color= color62 weight= 72 Dog.hascode= 246507189
Person : name= Bruce61 age= 71 Person.hascode= 1820524137 and Dog : category= category61 color= color61 weight= 71 Dog.hascode= 550370460
Person : name= Bruce60 age= 70 Person.hascode= 1820524135 and Dog : category= category60 color= color60 weight= 70 Dog.hascode= 864253591
Person : name= Bruce100 age= 110 Person.hascode= 601666520 and Dog : category= category100 color= color100 weight= 110 Dog.hascode= 2078199276
Person : name= Bruce69 age= 79 Person.hascode= 1820524153 and Dog : category= category69 color= color69 weight= 79 Dog.hascode= 1621196924
Person : name= Bruce68 age= 78 Person.hascode= 1820524151 and Dog : category= category68 color= color68 weight= 78 Dog.hascode= 184188532
Person : name= Bruce67 age= 77 Person.hascode= 1820524149 and Dog : category= category67 color= color67 weight= 77 Dog.hascode= 1132721997
Person : name= Bruce66 age= 76 Person.hascode= 1820524147 and Dog : category= category66 color= color66 weight= 76 Dog.hascode= 216072924
Person : name= Bruce65 age= 75 Person.hascode= 1820524145 and Dog : category= category65 color= color65 weight= 75 Dog.hascode= 142786591
===============================================Remove======================================
删除了category= category90 color= color90 weight= 100 Dog.hascode= 1157436341
删除了category= category91 color= color91 weight= 101 Dog.hascode= 1048575489
删除了category= category92 color= color92 weight= 102 Dog.hascode= 753416466
删除了category= category93 color= color93 weight= 103 Dog.hascode= 1879089963
删除了category= category94 color= color94 weight= 104 Dog.hascode= 1057945868
删除了category= category95 color= color95 weight= 105 Dog.hascode= 776412720
删除了category= category96 color= color96 weight= 106 Dog.hascode= 454535357
删除了category= category97 color= color97 weight= 107 Dog.hascode= 721042113
删除了category= category98 color= color98 weight= 108 Dog.hascode= 1988716027
删除了category= category99 color= color99 weight= 109 Dog.hascode= 977199748
删除了category= category100 color= color100 weight= 110 Dog.hascode= 2078199276
3.HashTable:线程安全的。
代码：
package com.work.eleven;
import java.util.HashSet;
import java.util.Hashtable;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
public class HashTableDemo {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Map<Person, Dog> pdmap = new Hashtable<Person, Dog>();
for (int i=1;i<11;i++){
pdmap.put(new Person("Bruce"+i,i+10), new Dog("color"+i, i+10,"category"+i));
}
System.out.println("===========keySet遍历==================");
Set<Person> personKeySet=pdmap.keySet();
for(Person person : personKeySet){
System.out.println("Person : "+person.toString()+" and Dog : "+pdmap.get(person).toString());
}
System.out.println("===========EntrySet遍历==================");
Set<Entry<Person, Dog>> personEntrySet =pdmap.entrySet();
for(Entry<Person, Dog> personEntry : personEntrySet){
System.out.println("Person : "+personEntry.getKey().toString()+" and Dog : "+personEntry.getValue().toString());
}
System.out.println("===========Remove==================");
Dog dog;
for(int j=1;j<5;j++){
dog= pdmap.remove(new Person("Bruce"+j,j+10));
System.out.println("删除了"+dog.toString());
}
System.out.println("剩余Dog数量 :"+pdmap.size()+" 只");
}
}
/*
运行结果：
===========keySet遍历==================
Person : name= Bruce5 age= 15 Person.hascode= 1998389245 and Dog : category= category5 color= color5 weight= 15 Dog.hascode= 1701381926
Person : name= Bruce4 age= 14 Person.hascode= 1998389243 and Dog : category= category4 color= color4 weight= 14 Dog.hascode= 1381270477
Person : name= Bruce3 age= 13 Person.hascode= 1998389241 and Dog : category= category3 color= color3 weight= 13 Dog.hascode= 714682869
Person : name= Bruce2 age= 12 Person.hascode= 1998389239 and Dog : category= category2 color= color2 weight= 12 Dog.hascode= 798941612
Person : name= Bruce1 age= 11 Person.hascode= 1998389237 and Dog : category= category1 color= color1 weight= 11 Dog.hascode= 1743911840
Person : name= Bruce10 age= 20 Person.hascode= 1820523930 and Dog : category= category10 color= color10 weight= 20 Dog.hascode= 1069480624
Person : name= Bruce9 age= 19 Person.hascode= 1998389253 and Dog : category= category9 color= color9 weight= 19 Dog.hascode= 322722178
Person : name= Bruce8 age= 18 Person.hascode= 1998389251 and Dog : category= category8 color= color8 weight= 18 Dog.hascode= 1595436971
Person : name= Bruce7 age= 17 Person.hascode= 1998389249 and Dog : category= category7 color= color7 weight= 17 Dog.hascode= 1028355155
Person : name= Bruce6 age= 16 Person.hascode= 1998389247 and Dog : category= category6 color= color6 weight= 16 Dog.hascode= 616699029
===========EntrySet遍历==================
Person : name= Bruce5 age= 15 Person.hascode= 1998389245 and Dog : category= category5 color= color5 weight= 15 Dog.hascode= 1701381926
Person : name= Bruce4 age= 14 Person.hascode= 1998389243 and Dog : category= category4 color= color4 weight= 14 Dog.hascode= 1381270477
Person : name= Bruce3 age= 13 Person.hascode= 1998389241 and Dog : category= category3 color= color3 weight= 13 Dog.hascode= 714682869
Person : name= Bruce2 age= 12 Person.hascode= 1998389239 and Dog : category= category2 color= color2 weight= 12 Dog.hascode= 798941612
Person : name= Bruce1 age= 11 Person.hascode= 1998389237 and Dog : category= category1 color= color1 weight= 11 Dog.hascode= 1743911840
Person : name= Bruce10 age= 20 Person.hascode= 1820523930 and Dog : category= category10 color= color10 weight= 20 Dog.hascode= 1069480624
Person : name= Bruce9 age= 19 Person.hascode= 1998389253 and Dog : category= category9 color= color9 weight= 19 Dog.hascode= 322722178
Person : name= Bruce8 age= 18 Person.hascode= 1998389251 and Dog : category= category8 color= color8 weight= 18 Dog.hascode= 1595436971
Person : name= Bruce7 age= 17 Person.hascode= 1998389249 and Dog : category= category7 color= color7 weight= 17 Dog.hascode= 1028355155
Person : name= Bruce6 age= 16 Person.hascode= 1998389247 and Dog : category= category6 color= color6 weight= 16 Dog.hascode= 616699029
===========Remove==================
删除了category= category1 color= color1 weight= 11 Dog.hascode= 1743911840
删除了category= category2 color= color2 weight= 12 Dog.hascode= 798941612
删除了category= category3 color= color3 weight= 13 Dog.hascode= 714682869
删除了category= category4 color= color4 weight= 14 Dog.hascode= 1381270477
剩余Dog数量 :6 只*/本文出自 “11138113” 博客，请务必保留此出处http://11148113.blog.51cto.com/11138113/1782557
原文地址：http://11148113.blog.51cto.com/11138113/1782557
