Guava:谷歌开发的集合库，通过build path->Add External JARs 把guava.jar包加进去。
版本控制工具：1.CVS 2.SVN 3.git
所以需要下载git客户端。
import com.google.common.collect.ImmutableList;
/**
* 只读设置
*/
public class Demo01 {
public static void main(String[] args) {
List list =new ArrayList();
list.add("a");
list.add("b");
list.add("c");
//对原有的list进行包装，相等于原有List的一个视图，快照，不够安全
List readList =Collections.unmodifiableList(list);
readList.add("d");//对这个视图增操作，错误，抛出java.lang.UnsupportedOperationException（不被支持的异常）。
list.add("d"); //正确，改变原有List，视图也一起改变，没有达到真正的目的，所以不够安全。
// guava对只读设置 安全可靠，并且相对简单
List immutableList =ImmutableList.of("a", "b", "c"); //初始化List
immutableList.add("d");//java.lang.UnsupportedOperationException
}
}
import com.google.common.base.Function;
import com.google.common.base.Functions;
import com.google.common.base.Predicate;
import com.google.common.collect.Collections2;
import com.google.common.collect.Lists;
import com.google.common.collect.Sets;
/**
* 函数式编程 :解耦
* 1、Predicate
* 2、Function
*
* 工具:Collections2.filter() 过滤器
* Collections2.transfer() 转换
* Functions.compose()组合式函数编程
*/
public class Demo02 {
public static void main(String[] args) {
//组合式函数编程
//确保容器中的字符串长度不超过5，超过进行截取，后全部大写
List list =Lists.newArrayList("bjsxt","good","happiness");//静态创建List，
//确保容器中的字符串长度不超过5，超过进行截取
Function f1 =new Function(){
@Override
public String apply(String input) {
return input.length()>5?input.substring(0,5):input;
}
};
//转成大写
Function f2 =new Function(){
@Override
public String apply(String input) {
return input.toUpperCase();
}
};
//String =f2(f1(String))
Function f =Functions.compose(f1, f2);
Collection resultCol =Collections2.transform(list, f);
for(String temp:resultCol){
System.out.println(temp);
}
}
/**
* 转换
*/
public static void test2(){
//类型转换
Set timeSet =Sets.newHashSet();
timeSet.add(10000000L);
timeSet.add(99999999999999999L);
timeSet.add(2000000000L);
Collection timeStrCol =Collections2.transform(timeSet, new Function(){
@Override
public String apply(Long input) {
return new SimpleDateFormat("yyyy-MM-dd").format(input);
}});
for(String temp:timeStrCol){
System.out.println(temp);
}
}
/**
* 过滤器
*/
public static void test1(){
//创建List 静态初始化
List list =Lists.newArrayList("moom","son","dad","bjsxt","refer");
//找出回文 palindrome backwords mirror words
//匿名内部类对象: 匿名内部类，同时创建类对象
Collection palindromeList =Collections2.filter(list, new Predicate(){
@Override
public boolean apply(String input) {//如果这个类只使用一次，并且这个类的对象也只使用一次，就用匿名内部类对象。
//业务逻辑
return new StringBuilder(input).reverse().toString().equals(input);//字符串的反转等于自身。
}
});
for(String temp:palindromeList){
System.out.println(temp);
}
}
}
import com.google.common.base.Preconditions;
import com.google.common.collect.Constraint;
import com.google.common.collect.Constraints;
import com.google.common.collect.Sets;
/**
* 加入约束条件:非空、长度验证
* Constraint
* Preconditions
* Constraints
*/
public class Demo03 {
public static void main(String[] args) {
Set sets =Sets.newHashSet();
//创建约束
Constraint constraint =new Constraint(){
@Override
public String checkElement(String element) {
//非空验证
Preconditions.checkNotNull(element);
//长度验证 5-20为字符串
Preconditions.checkArgument(element.length()>=5 && element.length()<=20);
return element;
}
};
Set cs =Constraints.constrainedSet(sets, constraint);
//cs.add(null); //java.lang.NullPointerException
//cs.add("good"); //java.lang.IllegalArgumentException
cs.add("bjsxt");
for(String str:cs){
System.out.println(str);
}
}
}
import com.google.common.collect.Sets;//谷歌的jar包
import com.google.common.collect.Sets.SetView;
/**
* 集合的操作:交集、差集、并集
* Sets.intersection()
* Sets.difference()
* Sets.union();
*/
public class Demo04 {
public static void main(String[] args) {
Set sets =Sets.newHashSet(1,2,3,4,5,6);
Set sets2 =Sets.newHashSet(3,4,5,6,7,8,9);
//交集
System.out.println("交集为:");
SetView intersection =Sets.intersection(sets, sets2);
for(Integer temp:intersection){
System.out.println(temp);//3456
}
//差集
System.out.println("差集为:");
SetView diff =Sets.difference(sets, sets2);
for(Integer temp:diff){
System.out.println(temp);//12
}
//并集
System.out.println("并集为:");
SetView union =Sets.union(sets, sets2);
for(Integer temp:union){
System.out.println(temp);//123456789
}
}
}
import com.google.common.collect.HashMultiset;
import com.google.common.collect.Multiset;
/**
* 统计单词出现的次数
* 1、HashMap 分拣存储+面向对象思维 -->判断
* 2、Multiset :无序+可重复 .count() 增强了可读性 +操作简单
* @author Administrator
*
*/
public class Demo05 {
public static void main(String[] args) {
String str ="this is a cat and that is a mice where is the food";
//分割字符串
String[] strArray =str.split(" ");
//存储到Multiset中
Multiset set =HashMultiset.create();
for(String strTemp:strArray){
set.add(strTemp);
}
//获取所有的单词 Set
Set letters =set.elementSet();
for(String temp:letters){
System.out.println(temp+"-->"+set.count(temp));//统计人员访问网站的 次数
}
/*mice-->1
that-->1
cat-->1
is-->3
food-->1
a-->2
the-->1
where-->1
this-->1
and-->1*/
}
}
import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.Multimap;
/**
* 分析查看 教师 教授的每门课程
* Multimap :key-value key可以重复
*/
public class Demo06 {
public static void main(String[] args) {
Map cours =new HashMap();
//加入测试数据
cours.put("改革开放", "邓爷爷");
cours.put("三个代表", "江主席");
cours.put("科学发展观", "胡主席");
cours.put("和谐社会", "胡主席");
cours.put("八荣八耻", "胡主席");
cours.put(".1..", "习主席");
cours.put("..2.", "习主席");
cours.put(".3..", "习主席");
//Multimap
Multimap teachers =ArrayListMultimap.create();
//迭代器
Iterator> it =cours.entrySet().iterator();
while(it.hasNext()){
Map.Entry entry =it.next();
String key =entry.getKey(); //课程
String value =entry.getValue(); //教师
//教师 -->课程
teachers.put(value, key);
}
//查看Multimap
Set keyset =teachers.keySet();
for(String key:keyset){
Collection col =teachers.get(key);
System.out.println(key+"-->"+col);
}
/*邓爷爷-->[改革开放]
江主席-->[三个代表]
习主席-->[.3.., ..2., .1..]
胡主席-->[科学发展观, 八荣八耻, 和谐社会]*/
}
}
import com.google.common.collect.BiMap;
import com.google.common.collect.HashBiMap;
/**
* HashMap 键唯一，值可以重复
* BiMap:双向Map(Bidirectional Map ) 键与值都不能重复(unique -valued map)
*/
public class Demo07 {
public static void main(String[] args) {
BiMap bimap=HashBiMap.create();
bimap.put("bjsxt", "[email protected]");
bimap.put("good","[email protected]");
//通过邮箱找用户
String user =bimap.inverse().get("[email protected]");
System.out.println(user);//good
System.out.println(bimap.inverse().inverse()==bimap);//true
}
}
import com.google.common.collect.HashBasedTable;
import com.google.common.collect.Table;
import com.google.common.collect.Table.Cell;
import com.google.common.collect.Tables;
/**
* 双键的Map -->Table -->rowKey+columnKey+value//类似于一个表格，2个作为key,另外一个作为value.
* 1、方法
* 所有的行数据:cellSet()
* 所有的学生: rowKeySet()//查看其中一列
* 所有的课程:columnKeySet()//查看另一列
* 所有的成绩: values()//查看所有的value
* 学生对应的课程: rowMap() +get(学生)
* row(学生)
* 课程对应的学生: columnMap +get(课程)
* column(课程)
*/
public class Demo08 {
public static void main(String[] args) {
Table tables=HashBasedTable.create();
//测试数据
tables.put("a", "javase", 80);
tables.put("b", "javase", 90);
tables.put("a", "oracle", 100);
tables.put("c", "oracle", 95);
//所有的行数据
Set> cells =tables.cellSet();
for(Cell temp:cells){
System.out.println(temp.getRowKey()+"-->"+temp.getColumnKey()+"-->"+temp.getValue());
}
System.out.println("==========学生查看成绩==============");
System.out.print("学生\t");
//所有的课程
Set cours =tables.columnKeySet();
for(String t:cours){
System.out.print(t+"\t");
}
System.out.println();
//所有的学生
Set stus =tables.rowKeySet();
for(String stu:stus){
System.out.print(stu+"\t");
Map scores =tables.row(stu);
for(String c:cours){
System.out.print(scores.get(c)+"\t");
}
System.out.println();
}
System.out.println("==========课程查看成绩==============");
System.out.print("课程\t");
//所有的学生
Set stuSet =tables.rowKeySet();
for(String t:stuSet){
System.out.print(t+"\t");
}
System.out.println();
//所有的课程
Set courSet =tables.columnKeySet();
for(String c:courSet){
System.out.print(c+"\t");
Map scores =tables.column(c);
for(String s:stuSet){
System.out.print(scores.get(s)+"\t");
}
System.out.println();
}
System.out.println("===========转换===========");
Table tables2 =Tables.transpose(tables);
//所有的行数据
Set> cells2 =tables2.cellSet();
for(Cell temp:cells2){
System.out.println(temp.getRowKey()+"-->"+temp.getColumnKey()+"-->"+temp.getValue());
}
}
}
import org.apache.commons.collections4.Predicate;
import org.apache.commons.collections4.PredicateUtils;
import org.apache.commons.collections4.functors.EqualPredicate;
import org.apache.commons.collections4.functors.NotNullPredicate;
import org.apache.commons.collections4.functors.UniquePredicate;
import org.apache.commons.collections4.list.PredicatedList;
/**
函数式编程 之 Predicate 断言
封装条件或判别式 if..else替代
1、 new EqualPredicate<类型>(值)
EqualPredicate.equalPredicate(值);
2、NotNullPredicate.INSTANCE
3、UniquePredicate.uniquePredicate()
4、自定义
new Predicate() +evaluate
PredicateUtils.allPredicate(可以传2个以上的断言器)，andPredicate(只能传2个断言器)，anyPredicate(多个断言器，只要其中一个 为true即可)
PredicatedXxx.predicatedXxx(容器,判断)
* @author Administrator
*
*/
public class Demo01 {
@SuppressWarnings("unchecked")
public static void main(String[] args) {
System.out.println("======自定义判断======");
//自定义的判别式
Predicate selfPre =new Predicate(){
@Override
public boolean evaluate(String object) {
return object.length()>=5 && object.length()<=20;
}};
Predicate notNull=NotNullPredicate.notNullPredicate();
Predicate all =PredicateUtils.allPredicate(notNull,selfPre);//多个断言器
List list =PredicatedList.predicatedList(new ArrayList(),all);//用这个断言器来限制容器。
list.add("bjsxt");
list.add(null);//报异常
list.add("bj");//报异常
}
/**
* 判断唯一
*/
public static void unique(){
System.out.println("====唯一性判断====");
Predicate uniquePre =UniquePredicate.uniquePredicate();
List list =PredicatedList.predicatedList(new ArrayList(), uniquePre);
list.add(100L);
list.add(200L);
list.add(100L); //出现重复值，抛出异常
}
/**
* 判断非空
*/
public static void notNull(){
System.out.println("====非空判断====");
Predicate notNull0 = NotNullPredicate.INSTANCE;
Predicate notNull = NotNullPredicate.notNullPredicate();
//String str ="bjs";
String str = null;
System.out.println(notNull.evaluate(str)); //如果非空为true ,否则为false
//添加容器值的判断
List list =PredicatedList.predicatedList(new ArrayList(), notNull);//要求容器list不能添加null值。
list.add(1000L);
list.add(null); //验证失败，出现异常
}
/**
* 比较相等判断
*/
public static void equal(){
System.out.println("======相等判断======");
Predicate pre0 =new EqualPredicate("bjsxt");//实例化一个对象
Predicate pre =EqualPredicate.equalPredicate("bjsxt");//创建对象
boolean flag =pre.evaluate("bj");//是否相等
System.out.println(flag);
}
}
import org.apache.commons.collections4.CollectionUtils;
import org.apache.commons.collections4.Predicate;
import org.apache.commons.collections4.Transformer;
import org.apache.commons.collections4.functors.SwitchTransformer;
/**
解耦，业务处理与判断进行分类
函数式编程 Transformer 类型转化
1、new Transformer() +transform
2、SwitchTransformer
CollectionUtils.collect(容器,转换器)
*/
public class Demo02 {
public static void main(String[] args) {
System.out.println("===自定义类型转换==");
//判别式
Predicate isLow=new Predicate(){//匿名内部类
@Override
public boolean evaluate(Employee emp) {
return emp.getSalary()<10000;
}
};
Predicate isHigh=new Predicate(){//匿名内部类
@Override
public boolean evaluate(Employee emp) {
return emp.getSalary()>=10000;
}
};
Predicate[] pres ={isLow,isHigh};
//转换，将Employee转成Level，
Transformer lowTrans =new Transformer(){
@Override
public Level transform(Employee input) {
return new Level(input.getName(),"卖身中");
}};
Transformer highTrans =new Transformer(){
@Override
public Level transform(Employee input) {
return new Level(input.getName(),"养身中");
}};
Transformer[] trans ={lowTrans,highTrans};
//二者进行了关联
Transformer switchTrans =new SwitchTransformer(pres, trans, null);
//容器
List list =new ArrayList();
list.add(new Employee("老马",1000000));
list.add(new Employee("老裴",999));
Collection levelList = CollectionUtils.collect(list,switchTrans);//参数为容器和转换规则
//遍历容器
Iterator levelIt =levelList.iterator();
while(levelIt.hasNext()){
System.out.println(levelIt.next());
/*(码农:老马,水平:养身中)
(码农:老裴,水平:卖身中)*/
}
}
/**
* 内置类型的转换
*/
public static void inner(){
System.out.println("===内置类型转换 长×××时间日期，转成指定格式的字符串==");
//类型转换器，将long类型转成String，
Transformer trans =new Transformer(){
@Override
public String transform(Long input) {
return new SimpleDateFormat("yyyy年MM月dd日").format(input);
}};
//容器
List list =new ArrayList();
list.add(999999999999L);
list.add(300000000L);
//工具类 ，程序猿出钱---开发商---农民工出力
Collection result=CollectionUtils.collect(list, trans);//将容器和类型转换器连接起来
//遍历查看结果
for(String time:result){
System.out.println(time);
}
}
}
/**
* 员工类
* @author Administrator
*
*/
public class Employee {
private String name;
private double salary;
//alt +/
public Employee() {
}
//alt+shift+s o
public Employee(String name, double salary) {
super();
this.name = name;
this.salary = salary;
}
//alt+shift+s +r tab 回车 shift+tab 回车
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public double getSalary() {
return salary;
}
public void setSalary(double salary) {
this.salary = salary;
}
@Override
public String toString() {
return "(码农:"+this.name+",敲砖钱:"+this.salary+")";
}
}
/**
* 等级类
* @author Administrator
*
*/
public class Level {
private String name;
private String level;
public Level() {
// TODO Auto-generated constructor stub
}
public Level(String name, String level) {
super();
this.name = name;
this.level = level;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getLevel() {
return level;
}
public void setLevel(String level) {
this.level = level;
}
@Override
public String toString() {
return "(码农:"+this.name+",水平:"+this.level+")";
}
}
import org.apache.commons.collections4.Closure;
import org.apache.commons.collections4.CollectionUtils;
import org.apache.commons.collections4.Predicate;
import org.apache.commons.collections4.functors.ChainedClosure;
import org.apache.commons.collections4.functors.IfClosure;
import org.apache.commons.collections4.functors.WhileClosure;
/**
函数式编程 Closure 闭包 封装特定的业务功能
1、Closure
2、IfClosure IfClosure.ifClosure(断言,功能1,功能2)
3、WhileClosure WhileClosure.whileClosure(断言,功能,标识)
4、ChainedClosure.chainedClosure(功能列表);
CollectionUtils.forAllDo(容器,功能类对象);
*/
public class Demo03 {
public static void main(String[] args) {
basic();
ifClosure();
whileClosure();
chainClosure();
}
/**
* 折上减 先打折商品，进行9折，满百再减20
*/
public static void chainClosure(){
List goodsList =new ArrayList();
goodsList.add(new Goods("javase视频1",120,true));
goodsList.add(new Goods("javaee视频2",100,false));
goodsList.add(new Goods("高新技术视频",80,false));
//满百减20
Closure subtract=new Closure(){
public void execute(Goods goods) {
if(goods.getPrice()>=100){
goods.setPrice(goods.getPrice()-20);
}
}};
//打折
Closure discount=new Closure(){
public void execute(Goods goods) {
if(goods.isDiscount()){
goods.setPrice(goods.getPrice()*0.9);
}
}};
//链式操作
Closure chainClo=ChainedClosure.chainedClosure(discount,subtract);
//关联
CollectionUtils.forAllDo(goodsList,chainClo);
//查看操作后的数据
for(Goods temp:goodsList){
System.out.println(temp);
/*(商品:javase视频1,价格:88.0,是否打折:是)
(商品:javaee视频2,价格:80.0,是否打折:否)
(商品:高新技术视频,价格:80.0,是否打折:否)*/
}
}
/**
* 确保所有的员工工资都大于10000,如果已经超过的不再上涨
*/
public static void whileClosure(){
//数据
List empList =new ArrayList();
empList.add(new Employee("bjsxt",20000));
empList.add(new Employee("is",10000));
empList.add(new Employee("good",5000));
//业务功能 每次上涨0.2
Closure cols=new Closure(){
public void execute(Employee emp) {
emp.setSalary(emp.getSalary()*1.2);
}};
//判断
Predicate empPre=new Predicate(){
@Override
public boolean evaluate(Employee emp) {
return emp.getSalary()<10000;
}
};
//false 表示 while结构 先判断后执行 true do..while 先执行后判断
Closure whileCols =WhileClosure.whileClosure(empPre, cols, false);//empPre为true则进入cols，
//工具类
CollectionUtils.forAllDo(empList, whileCols) ;
//操作后的数据
Iterator empIt=empList.iterator();
while(empIt.hasNext()){
System.out.println(empIt.next());
/*(码农:bjsxt,敲砖钱:20000.0)
(码农:is,敲砖钱:10000.0)
(码农:good,敲砖钱:10368.0) 涨到超过一万为止。*/
}
}
/**
* 二选一 如果是打折商品，进行9折，否则满百减20
*/
public static void ifClosure(){
List goodsList =new ArrayList();
goodsList.add(new Goods("javase视频1",120,true));
goodsList.add(new Goods("javaee视频2",100,false));
goodsList.add(new Goods("高新技术视频",80,false));
//满百减20
Closure subtract=new Closure(){
public void execute(Goods goods) {
if(goods.getPrice()>=100){
goods.setPrice(goods.getPrice()-20);
}
}};
//打折
Closure discount=new Closure(){
public void execute(Goods goods) {
if(goods.isDiscount()){
goods.setPrice(goods.getPrice()*0.9);
}
}};
//判断
Predicate pre=new Predicate(){
public boolean evaluate(Goods goods) {
return goods.isDiscount();
}};
//二选一
Closure ifClo=IfClosure.ifClosure(pre,subtract,discount);
//关联
CollectionUtils.forAllDo(goodsList,ifClo);
//查看操作后的数据
for(Goods temp:goodsList){
System.out.println(temp);
/*(商品:javase视频,价格:108.0,是否打折:是)
(商品:javaee视频,价格:80.0,是否打折:否)
(商品:高新技术视频,价格:80.0,是否打折:否)*/
}
}
/**
* 基本操作
*/
public static void basic(){
//数据
List empList =new ArrayList();
empList.add(new Employee("bjsxt",20000));
empList.add(new Employee("is",10000));
empList.add(new Employee("good",5000));
//业务功能
Closure cols=new Closure(){//匿名内部类对象
public void execute(Employee emp) {
emp.setSalary(emp.getSalary()*1.2);//工资加倍
}};
//工具类
CollectionUtils.forAllDo(empList, cols) ;
//操作后的数据
Iterator empIt=empList.iterator();
while(empIt.hasNext()){
System.out.println(empIt.next());
/*(码农:bjsxt,敲砖钱:24000.0)
(码农:is,敲砖钱:12000.0)
(码农:good,敲砖钱:6000.0)*/
}
}
}
public class Goods {
private String name;
private double price;
//折扣
private boolean discount;
public Goods() {
// TODO Auto-generated constructor stub
}
public Goods(String name, double price, boolean discount) {
super();
this.name = name;
this.price = price;
this.discount = discount;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public double getPrice() {
return price;
}
public void setPrice(double price) {
this.price = price;
}
public boolean isDiscount() {
return discount;
}
public void setDiscount(boolean discount) {
this.discount = discount;
}
@Override
public String toString() {
return "(商品:"+this.name+",价格:"+this.price+",是否打折:"+(discount?"是":"否")+")";
}
}
import org.apache.commons.collections4.CollectionUtils;
/**
* 集合操作
* 1、并集
* CollectionUtils.union();
* 2、交集
* CollectionUtils.intersection();
* CollectionUtils.retainAll();
* 3、差集
* CollectionUtils.subtract();
*/
public class Demo04 {
public static void main(String[] args) {
Set set1 =new HashSet();
set1.add(1);
set1.add(2);
set1.add(3);
Set set2 =new HashSet();
set2.add(2);
set2.add(3);
set2.add(4);
//并集
System.out.println("=========并集============");
Collection col =CollectionUtils.union(set1,set2);
for(Integer temp:col){
System.out.println(temp);
}
//交集
System.out.println("=========交集============");
//col =CollectionUtils.intersection(set1, set2);
col =CollectionUtils.retainAll(set1, set2);
for(Integer temp:col){
System.out.println(temp);
}
//差集
System.out.println("=========差集============");
col =CollectionUtils.subtract(set1, set2);
for(Integer temp:col){
System.out.println(temp);
}
}
}
队列：
import java.util.Queue;
import org.apache.commons.collections4.Predicate;
import org.apache.commons.collections4.functors.NotNullPredicate;
import org.apache.commons.collections4.queue.CircularFifoQueue;
import org.apache.commons.collections4.queue.PredicatedQueue;
import org.apache.commons.collections4.queue.UnmodifiableQueue;
/**
Queue队列(先进先出)，栈(后进先出)
1、循环队列:CircularFifoQueue
2、只读队列:不可改变队列 UnmodifiableQueue
3、断言队列:PredicatedQueue.predicatedQueue()
*/
public class Demo05 {
public static void main(String[] args) {
circular();
readOnly();
predicate();
}
/**
* 断言队列
*/
public static void predicate(){
//循环队列
CircularFifoQueue que =new CircularFifoQueue(2);
que.add("a");
que.add("b");
que.add("c");
Predicate notNull=NotNullPredicate.INSTANCE;
//包装成对应的队列
Queue que2=PredicatedQueue.predicatedQueue(que, notNull);
que2.add(null);
}
/**
* 只读队列
*/
public static void readOnly(){
//循环队列
CircularFifoQueue que =new CircularFifoQueue(2);
que.add("a");
que.add("b");
que.add("c");
Queue readOnlyQue =UnmodifiableQueue.unmodifiableQueue(que);
readOnlyQue.add("d");
}
/**
* 循环队列
*/
public static void circular(){
//循环队列
CircularFifoQueue que =new CircularFifoQueue(2);
que.add("a");
que.add("b");
que.add("c");
//查看
for(int i=0;i it0 =new ArrayListIterator(arr);
//指定起始索引和结束索引
Iterator it =new ArrayListIterator(arr,1,3);
while(it.hasNext()){
System.out.println(it.next());//2，3
}
}
/**
* 循环迭代器
*/
public static void loopIt(){
System.out.println("===== 循环迭代器 ====");
List list =new ArrayList();
list.add("refer");
list.add("dad");
list.add("bjsxt");
list.add("moom");
Iterator it =new LoopingIterator(list);
for(int i=0;i<8;i++){
System.out.println(it.next());
/*refer
dad
bjsxt
moom
refer
dad
bjsxt
moom*/
}
}
/**
* 自定义迭代器
*/
public static void filterIt(){
System.out.println("=====自定义迭代器 ====");
List list =new ArrayList();
list.add("refer");
list.add("dad");
list.add("bjsxt");
list.add("moom");
//自定义条件判断
Predicate pre =new Predicate(){
public boolean evaluate(String value) {
//回文判断
return new StringBuilder(value).reverse().toString().equals(value);
}};
//去除重复的过滤器
Iterator it =new FilterIterator(list.iterator(),pre);
while(it.hasNext()){
System.out.println(it.next());
/*refer
dad
moom*/
}
}
/**
* 去重迭代器
*/
public static void uniqueIt(){
System.out.println("=====去重迭代器 ====");
List list =new ArrayList();
list.add("a");
list.add("b");
list.add("a");
//去除重复的过滤器
Iterator it =new UniqueFilterIterator(list.iterator());
while(it.hasNext()){
System.out.println(it.next());
/*a
b*/
}
}
/**
* map迭代器
*/
public static void mapIt(){
System.out.println("=====map迭代器====");
IterableMap map =new HashedMap();
map.put("a","bjsxt");
map.put("b", "sxt");
map.put("c", "good");
//使用 MapIterator
MapIterator it =map.mapIterator();
while(it.hasNext()){
String key =it.next();
String value =it.getValue();
System.out.println(key+"-->"+value);
/*a-->bjsxt
c-->good
b-->sxt*/
}
}
}
import org.apache.commons.collections4.BidiMap;
import org.apache.commons.collections4.MapIterator;
import org.apache.commons.collections4.bidimap.DualHashBidiMap;
import org.apache.commons.collections4.bidimap.DualTreeBidiMap;
/**
双向Map 要求键与值都不能重复
接口BidiMap inverseBidiMap()
实现类1、DualTreeBidiMap :有序
实现类2、DualHashBidiMap :无序
*/
public class Demo07 {
public static void main(String[] args) {
hashMap();
treeMap();
}
/**
* 有序的双向Map(key会自动排列)
*/
public static void treeMap(){
System.out.println("=====有序的双向Map====");
BidiMap map =new DualTreeBidiMap();
map.put("zbj", "[email protected]");
map.put("sxt", "[email protected]");//{[email protected], [email protected]}
//遍历查看
MapIterator it =map.inverseBidiMap().mapIterator();//{[email protected]=zbj, [email protected]=sxt}
while(it.hasNext()){
String key =it.next();
String value =it.getValue();
System.out.println(key+"-->"+value);
//[email protected]>zbj
//[email protected]>sxt
}
}
/**
* 无序的双向Map
*/
public static void hashMap(){
System.out.println("=====无序的双向Map====");
BidiMap map =new DualHashBidiMap();
map.put("bj", "[email protected]");
map.put("sxt", "[email protected]");//{[email protected], [email protected]}
//反转
System.out.println(map.inverseBidiMap().get("[email protected]"));//先要反转，然后通过value找到key,sxt
//遍历查看
MapIterator it =map.inverseBidiMap().mapIterator();//{[email protected]=sxt, [email protected]=bj}
while(it.hasNext()){
String key =it.next();
String value =it.getValue();
System.out.println(key+"-->"+value);
/*[email protected]>sxt
[email protected]>bj*/
}
}
}
import org.apache.commons.collections4.Bag;
import org.apache.commons.collections4.bag.HashBag;
import org.apache.commons.collections4.bag.TreeBag;
/**
接口Bag 包 允许重复
实现类1、HashBag 无序
实现类2、TreeBag 有序
统计单词的出现次数
*/
public class Demo08 {
/**
* @param args
*/
public static void main(String[] args) {
hashBag();
treeBag();
String str ="this is a cat and that is a mice where is the food";
//分割字符串
String[] strArray =str.split(" ");
Bag bag =new TreeBag();
for(String temp:strArray){
bag.add(temp);//[2:a,1:and,1:cat,1:food,3:is,1:mice,1:that,1:the,1:this,1:where]
}
System.out.println("====统计次数===");
Set keys =bag.uniqueSet();//[a, and, cat, food, is, mice, that, the, this, where]
for(String letter:keys){
System.out.println(letter+"-->"+bag.getCount(letter));
/*a-->2
and-->1
cat-->1
food-->1
is-->3
mice-->1
that-->1
the-->1
this-->1
where-->1*/
}
}
/**
* 有序
*/
public static void treeBag(){
System.out.println("=====有序的包====");
Bag bag =new TreeBag();
bag.add("a");
bag.add("a",5);
bag.remove("a", 2);
bag.add("b");
bag.add("c");//[4:a,1:b,1:c],有序
Iterator it =bag.iterator();
while(it.hasNext()){
System.out.println(it.next());//aaaabc
}
}
/**
* 无序
*/
public static void hashBag(){
System.out.println("=====无序的包====");
Bag bag =new HashBag();
bag.add("a");
bag.add("a",5);//加5次a,[6:a]
bag.remove("a", 2);//移除2个a,[4:a]
bag.add("b");
bag.add("c");//[1:b,1:c,4:a],一个b,一个c,4个a,
Iterator it =bag.iterator();
while(it.hasNext()){
System.out.println(it.next());//bcaaaa
}
}
}
总结：
set没有顺序，顺序指的是索引的顺序不是指内容。
1.迭代器：Iterator，
2.比较器：实体类可以排序（实现Comparable重写compareTo），还可以用排序比较器（实现Comparator重写compare），TreeSet、TreeMap.
3.泛型：反泛型类，泛型方法，泛型接口，泛型擦出，通配符？
4.6个接口：Collection，set,List,Map,Iterator,Comparable
5.9个常用类：
1)
查看多余修改时推荐使用ArrayList（add,remove,set(修改),get,foreach,）。
2)
修改多余查看推荐使用LinkList,多了链头与链尾的方法。
3)HashSet：元素不能重复，所以要求元素要重写hashCode和equals方法.
4)Treeset:要求元素可以排序或者提供排序的业务类。
5)HashMap:键不能重复必须重写hashCode和equals方法，值可以重复，put(),remove(),get().
6)Properties:资源配置文件，
7)Hashtable:键与值都不能为null,
8)Stack:栈
9)Collections:工具类
原文链接：https://www.cnblogs.com/yaowen/p/4833576.html