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Apache Commons Collections基本操作（Predicate、Transformat、Closure等）

2020-09-19 分类：博客 阅读(272) 评论(0) 扫描二维码 隐藏侧边

一、Predicate断言

package Collections;

import java.util.ArrayList;
import java.util.List;

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.notNullPredicate * NotNullPredicate.INSTANCE * * PredicatedList.predicatedXxx(容器，判断) * * 3、 UniquePredicate.uniquePredicate() * * 4、 自定义 new Predicate类 + 重写evaluate方法 * PredicateUtils.allPredicate 多于两个 * andPredicate 两个 * anyPredicate 其中一个 * */
@SuppressWarnings("all")
public class Demo01 {
    public static void main(String[] args) {
        Test001();
        Test002();
        Test003();
        Test004();      
    }

    /** * 比较相等判断 */
   public static void Test001()
   {
        System.out.println("=====相等判断=======");
        Predicate<String> pre = new EqualPredicate<String>("liguodong");
        //Predicate<String> pre = EqualPredicate.equalPredicate("liguodong");//同上
        boolean flag = pre.evaluate("li");
        System.out.println(flag);       
   }


   /** * 非空判断 */
   public static void Test002()
   {
        System.out.println("=====非空判断=======");
        Predicate  notNull = NotNullPredicate.INSTANCE;
        //Predicate notNull = NotNullPredicate.notNullPredicate();//同上
        String str = "lgd";
        System.out.println(notNull.evaluate(str));//非空为true,否则为false。

        //添加容器值得判断
        List<Long> list = PredicatedList.predicatedList(new ArrayList<>(), notNull);
        list.add(1000L);
        //list.add(null);//null值为false， 验证失败，出现异常
   }


   public static void Test003()
    {
        System.out.println("=====唯一性判断=======");
        Predicate<Long> uniquePre = UniquePredicate.uniquePredicate();      
        List<Long> list = PredicatedList.predicatedList(new ArrayList<Long>(),uniquePre);
        list.add(100L);
        list.add(200L);
        //list.add(100L);//出现重复值，抛出异常

    }


   public static void Test004(){
       System.out.println("=====自定义判断=======");
        //自定义的判别式
        Predicate<String> selfPre = new Predicate<String>() {
            @Override
            public boolean evaluate(String object) {
                return object.length()>=5&&object.length()<=20;
            }       
        };

        Predicate notNull = NotNullPredicate.notNullPredicate();//非空

        Predicate all = PredicateUtils.allPredicate(selfPre,notNull);       
        List<String> list = PredicatedList.predicatedList(new ArrayList<>(), all);
        list.add("liguodong");
        //list.add(null);//java.lang.NullPointerException
        //list.add("byby");//java.lang.IllegalArgumentException
   }
}

运行结果：

=====相等判断======= false
=====非空判断======= true
=====唯一性判断======= =====自定义判断=======

二、Transformat 类型转换

package Collections;
/** * 员工类 */
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+",薪水："+this.salary+")";
    }

}

package Collections;

public class Level {
    private String name;
    private String level;
    public Level() {
    }
    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+")";
    }
}
package Collections;

import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;

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：将 业务处理与判断进行分离 * * 函数式编程Transformat 类型转换 * 1.Transformer+CollectionUtils.collect * * 2.SwitchTransformer * CollectionUtils.collect(容器，转换器) */

@SuppressWarnings("all")
public class Demo02 {   
    public static void main(String[] args) {
        inner();
        define();
    }

    //内置类型的转化
    public static void inner()
    {
        System.out.println("========《内置类型转换 长整型时间日期，转成指定格式的字符串》========");
        //类型转换器
        Transformer<Long,String> trans = new Transformer<Long,String>()
        {
            @Override
            public String transform(Long input) {
                return new SimpleDateFormat("yyyy年MM月dd日").format(input);
            }

        };

        //容器
        List<Long> list = new ArrayList<>();
        list.add(99999999L);
        list.add(30000L);

        //工具类：程序员出钱<---开发商--->农民工出力
        Collection<String> result = CollectionUtils.collect(list, trans);

        //遍历查看结果
        for(String time:result){
            System.out.println(time);
        }
    }

    //自定义类型转换
    public static void define(){
        System.out.println("==========《自定义类型转换》===========");

        Predicate<Employee> isLow = new Predicate<Employee>(){
            public boolean evaluate(Employee emp)
            {
                return emp.getSalary()<=10000;
            }
        };              
        Predicate<Employee> isHigh = new Predicate<Employee>() {
            public boolean evaluate(Employee emp)
            {
                return emp.getSalary()>=10000;
            }
        };  
        Predicate[] pres = {isLow,isHigh};


        //转换
        Transformer<Employee,Level> lowtrans = new Transformer<Employee,Level>()
        {   
            @Override
            public Level transform(Employee input) {
                return new Level(input.getName(),"低薪");
            }
        };              
        //转换
        Transformer<Employee,Level> hightrans = new Transformer<Employee,Level>()
        {   
            @Override
            public Level transform(Employee input) {
                return new Level(input.getName(),"高薪");
            }
        };      
        Transformer[] trans = {lowtrans,hightrans};


        //二者进行了关联
        Transformer switchTrans = new SwitchTransformer<>(pres, trans, null);

        List<Employee> list = new ArrayList<>();
        list.add(new Employee("凤姐",10000000));
        list.add(new Employee("犀利哥",1000));

        Collection<Level> levelList = CollectionUtils.collect(list, switchTrans);

        //遍历容器
        Iterator<Level> levelIt = levelList.iterator();
        while(levelIt.hasNext())
        {
            System.out.println(levelIt.next());
        }
    }
}

运行结果：

========《内置类型转换 长整型时间日期，转成指定格式的字符串》======== 1970年01月02日
1970年01月01日
==========《自定义类型转换》=========== (码农：凤姐,水平:高薪)
(码农：犀利哥,水平:低薪)

三、Closure 闭包封装业务功能

package Collections;
/** * 员工类 */
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+",薪水："+this.salary+")";
    }

}
package Collections;

public class Goods {
    private String name;
    private double price;
    private boolean discount;//折扣
    public Goods() {
    }
    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")+")";      
    }
}
package Collections;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

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 闭包封装业务功能 * 1. Closure * CollectionUtils.forAllDo(容器,功能类对象) * * 2. IfClosure * IfClosure.ifClosure(断言，功能1，功能2) * CollectionUtils.forAllDo(容器,功能类对象) * * 3. WhileClosure * WhileClosure.whileClosure(断言,功能，标识符) * CollectionUtils.forAllDo(容器,功能类对象) * * 4. ChainedClosure * ChainedClosure.chainedClosure(功能列表) * CollectionUtils.forAllDo(容器，功能类对象) * @author liguodong */

@SuppressWarnings("all")
public class Demo03 {
    public static void main(String[] args) {
        basic();
        System.out.println("==================");
        ifClousure();
        System.out.println("==================");
        whileClosure();
        System.out.println("==================");
        chainClousure();
    }


    //基本操作
    public static void basic()
    {
        //数据
        List<Employee> empList = new ArrayList<>();
        empList.add(new Employee("mark",20000));
        empList.add(new Employee("json",10000));
        empList.add(new Employee("Ivy",5000));

        //业务功能
        Closure<Employee> cols = new Closure<Employee>()
        {
            @Override
            public void execute(Employee emp) {
                emp.setSalary(emp.getSalary()*1.2);
            }

        };

        //工具类
        CollectionUtils.forAllDo(empList, cols);        

        //操作后的数据
        Iterator<Employee> empIt = empList.iterator();
        while(empIt.hasNext())
        {
            System.out.println(empIt.next());
        }
    }


    /** * 二选一 如果打折商品，进行9折；否则满百减20。 */
    public static void ifClousure()
    {
        List<Goods> goodsList = new ArrayList<>();
        goodsList.add(new Goods("android视频",120,true));
        goodsList.add(new Goods("javaee视频",80,false));
        goodsList.add(new Goods("hadoop视频",150,false));

        //满百减20
        Closure<Goods> subtract = new Closure<Goods>() {
            @Override
            public void execute(Goods input) {
                if(input.getPrice()>=100){
                    input.setPrice(input.getPrice()-20);
                }           
            }
        };

        //打折
        Closure<Goods> discount = new Closure<Goods>() {
            @Override
            public void execute(Goods input) {
                if(input.isDiscount()){
                    input.setPrice(input.getPrice()*0.9);
                }           
            }
        };

        //判断
        Predicate<Goods> pre = new Predicate<Goods>() {
            @Override
            public boolean evaluate(Goods goods) {
                return goods.isDiscount();
            }
        };

        //二选一
        Closure<Goods> ifClo = IfClosure.ifClosure(pre,discount,subtract);

        //关联
        CollectionUtils.forAllDo(goodsList,ifClo);  

        //查看操作后的数据
        for(Goods temp:goodsList)
        {
            System.out.println(temp);
        }
    }



    /** * 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<Employee> empList = new ArrayList<>();
        empList.add(new Employee("周杰伦",20000));
        empList.add(new Employee("范冰冰",30000));
        empList.add(new Employee("黄晓明",5000));

        //业务功能 每次上涨0.2
        Closure<Employee> cols = new Closure<Employee>()
        {
            @Override
            public void execute(Employee emp) {
                emp.setSalary(emp.getSalary()*1.2);
            }

        };

        //判断
        Predicate<Employee> empPre = new Predicate<Employee>() {
            @Override
            public boolean evaluate(Employee emp) {
                return emp.getSalary()<10000;
            }
        };

        //false 表示while结构先判断后执行 
        //true 表示do..while先执行后判断
        Closure<Employee> whileCols = WhileClosure.whileClosure(empPre,cols,false); 


        //工具类
        CollectionUtils.forAllDo(empList, whileCols);

        //操作后的数据
        Iterator<Employee> empIt = empList.iterator();
        while(empIt.hasNext())
        {
            System.out.println(empIt.next());
        }
    }   



    /** *折上减 如果打折商品，先进行9折，如果还满百，再减20 */
    public static void chainClousure()
    {
        List<Goods> goodsList = new ArrayList<>();
        goodsList.add(new Goods("Android视频",120,true));
        goodsList.add(new Goods("javaee视频",100,false));
        goodsList.add(new Goods("Spack视频",80,false));

        //满百减20
        Closure<Goods> subtract = new Closure<Goods>() {
            @Override
            public void execute(Goods input) {
                if(input.getPrice()>=100){
                    input.setPrice(input.getPrice()-20);
                }
            }
        };

        //打折
        Closure<Goods> discount = new Closure<Goods>() {
            @Override
            public void execute(Goods input) {
                if(input.isDiscount()){
                    input.setPrice(input.getPrice()*0.9);
                }           
            }
        };

        //链式操作
        Closure<Goods> chinaClo = ChainedClosure.chainedClosure(discount,subtract);

        //关联
        CollectionUtils.forAllDo(goodsList,chinaClo);

        //查看操作后的数据
        for(Goods temp:goodsList)
        {
            System.out.println(temp);
        }
    }
}

运行结果：

(码农：mark,薪水：24000.0)
(码农：json,薪水：12000.0)
(码农：Ivy,薪水：6000.0) ==================
(商品:android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:hadoop视频，价格：130.0,是否打折：否) ==================
(码农：周杰伦,薪水：20000.0)
(码农：范冰冰,薪水：30000.0)
(码农：黄晓明,薪水：10368.0) ==================
(商品:Android视频，价格：88.0,是否打折：是)
(商品:javaee视频，价格：80.0,是否打折：否)
(商品:Spack视频，价格：80.0,是否打折：否)

四、集合操作

package Collections;

import java.util.Collection;
import java.util.HashSet;
import java.util.Set;

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<Integer> set1 = new HashSet<>();
        set1.add(1);
        set1.add(2);
        set1.add(3);

        Set<Integer> set2 = new HashSet<>();
        set2.add(2);
        set2.add(3);
        set2.add(4);
        System.out.println("========并集==========");
        //并集
        Collection<Integer> col = CollectionUtils.union(set1, set2);
        for(Integer temp:col)
        {
            System.out.print(temp+" ");
        }
        System.out.println("\n=========交集=========");
        //交集
        //col  = CollectionUtils.intersection(set1, set2);
        col  = CollectionUtils.retainAll(set1, set2);
        for(Integer temp:col)
        {
            System.out.print(temp+" ");
        }       
        //差集
        System.out.println("\n=========差集=========");
        col  = CollectionUtils.subtract(set1, set2);
        for(Integer temp:col)
        {
            System.out.print(temp+" ");
        }       
    }
}

运行结果：

========并集========== 1 2 3 4 
=========交集========= 2 3 
=========差集========= 1

五、Queue队列

package Collections;

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 * 1.循环队列 * 2.只读队列：不可改变队列 */
@SuppressWarnings("all")
public class Demo05 {
    public static void main(String[] args) {
        circullar();
        readOnly();
        //predicate();
    }

    /** * 循环队列 */
    public static void circullar()
    {
        //长度是2，因此只能保留两个，循环着走。
        CircularFifoQueue<String> que = new CircularFifoQueue<>(2);
        que.add("a");
        que.add("b");
        que.add("c");
        que.add("d");
        //查看
        for(int i=0;i<que.size();i++)
        {
            System.out.println(que.get(i));
        }
    }
    /** * 只读队列 */
    public static void readOnly()
    {
        CircularFifoQueue<String> que = new CircularFifoQueue<>(2);
        que.add("a");
        que.add("b");
        que.add("c");
        Queue<String> readOnlyOne = UnmodifiableQueue.unmodifiableQueue(que);
        //readOnlyOne.add("d");//java.lang.UnsupportedOperationException
    }

    /** * 断言队列 */
    public static void predicate()
    {
        //循环队列
        CircularFifoQueue<String> 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<String> que2 = PredicatedQueue.predicatedQueue(que,notNull);
        //que2.add(null);//java.lang.IllegalArgumentException
    }
}

运行结果：

c
d

六、迭代器的扩展

package Collections;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import org.apache.commons.collections4.IterableMap;
import org.apache.commons.collections4.MapIterator;
import org.apache.commons.collections4.Predicate;
import org.apache.commons.collections4.iterators.ArrayListIterator;
import org.apache.commons.collections4.iterators.FilterIterator;
import org.apache.commons.collections4.iterators.LoopingIterator;
import org.apache.commons.collections4.iterators.UniqueFilterIterator;
import org.apache.commons.collections4.map.HashedMap;

/** * 迭代器的扩展 * 1、MapIterator 以后不再使用map.keySet.iterator访问 * IterableMap * HashedMap * 2、去重迭代器 * UniqueFilterIterator * 3、自定义的过滤器 * FilterIterator 自定义的过滤器+Predicate * 4、循环迭代器 * LoopingIterator * 5、数组迭代器 * ArrayListIterator * * @author liguodong */
@SuppressWarnings("all")
public class Demo06 {


    public static void main(String[] args) {
        mapIt();
        uniqueIt();
        filterIt();
        loopIt();
        arrayIt();
    }
    /** * map迭代器 */
    public static void mapIt()
    {
        System.out.println("=======map迭代器=========");
        IterableMap<String,String> map = new HashedMap<>();     
        map.put("a", "baby");
        map.put("b", "ohyeah");
        map.put("c", "doog");

        //使用MapIterator
        MapIterator<String,String> it = map.mapIterator();
        while(it.hasNext())
        {
            //移动游标 it.next()
            String key = it.next();
            //或者使用如下方法
            /*it.next(); String key = it.getKey();*/

            String value = it.getValue();
            System.out.println(key+"-->"+value);            
        }
    }

    /** * 去重迭代器 */
    public static void uniqueIt()
    {
        System.out.println("=======去重迭代器=========");
        List<String> list = new ArrayList<>();
        list.add("a");
        list.add("b");
        list.add("a");
        //去掉重复的过滤器
        Iterator<String> it = new UniqueFilterIterator<>(list.iterator());
        while(it.hasNext())
        {
            System.out.println(it.next());
        }
    }

    /** * 自定义迭代器 */
    public static void filterIt()
    {
        System.out.println("======= 自定义迭代器=========");
        List<String> list = new ArrayList<>();
        list.add("abcba");
        list.add("dad");
        list.add("dsfa");
        //自定义的条件
        Predicate<String> pre = new Predicate<String>() {
            @Override
            public boolean evaluate(String value) {
                //回文判断
                return new StringBuilder(value).reverse().toString().equals(value);
            }
        };

        //去重重复的过滤器
        Iterator<String> it = new FilterIterator(list.iterator(),pre);
        while(it.hasNext())
        {
            System.out.println(it.next());
        }
    }

    /** * 循环迭代器 */
    public static void loopIt()
    {
        System.out.println("======= 循环迭代器=========");
        List<String> list = new ArrayList<>();
        list.add("refer");
        list.add("dad");
        list.add("sdafds"); 

        Iterator<String> it = new LoopingIterator<>(list);      
        for(int i=0;i<5;i++)
        {
            System.out.println(it.next());
        }
    }


    /** * 数组迭代器 */
    public static void arrayIt()
    {
        System.out.println("=======数组迭代器=========");
        int[] str = {1,2,3,4,5};

        //Iterator<Integer> it = new ArrayListIterator<>(str);

        //也可以指定起始索引和结束索引
        Iterator<Integer> it = new ArrayListIterator<>(str,1,3);
        while(it.hasNext())
        {
            System.out.println(it.next());
        }       
    }   
}

运行结果：

=======map迭代器========= a-->baby
c-->doog
b-->ohyeah
=======去重迭代器========= a
b
======= 自定义迭代器========= abcba
dad
======= 循环迭代器========= refer
dad
sdafds
refer
dad
=======数组迭代器========= 2
3

七、双向Map

package Collections;

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 * BidiMap接口 inverseBidiMap()反转方法 * 1、DualTreeBidiMap:有序 * 2、DualHashBidiMp:无序 */
public class Demo07 {
    public static void main(String[] args) {
        hashMap();
        treeMap();
    }   
    /** * 无序的双向Map */ 
    public static void hashMap()
    {
        System.out.println("=======无序的双向Map=========");
        BidiMap<String, String> map = new DualHashBidiMap<>();
        map.put("bj", "bj@test.com");
        map.put("ddssf", "ssdsfdsj@126.com");
        map.put("dsf", "bfdsfdsj@qq.com");
        //反转
        System.out.println(map.inverseBidiMap().get("bj@test.com"));

        //遍历查看
        MapIterator<String, String> it = map.inverseBidiMap().mapIterator();
        while(it.hasNext())
        {
            String key = it.next();
            String value = it.getValue();
            System.out.println(key+"-->"+value);
        }
    }

    /** * 有序的双向Map */
    public static void treeMap()
    {
        System.out.println("=======有序的双向Map=========");
        BidiMap<String, String> map = new DualTreeBidiMap<>();
        map.put("bj", "bj@test.com");
        map.put("ddssf", "ssdsfdsj@126.com");
        map.put("dsf", "bfdsfdsj@qq.com");

        //遍历查看
        MapIterator<String, String> it = map.inverseBidiMap().mapIterator();
        while(it.hasNext())
        {
            String key = it.next();
            String value = it.getValue();
            System.out.println(key+"-->"+value);
        }
    }
}

运行结果：

=======无序的双向Map=========
bj
ssdsfdsj@126.com-->ddssf
bfdsfdsj@qq.com-->dsf
bj@test.com-->bj
=======有序的双向Map=========
bfdsfdsj@qq.com-->dsf
bj@test.com-->bj
ssdsfdsj@126.com-->ddssf

八、Bag包

package Collections;

import java.util.Iterator;
import java.util.Set;

import org.apache.commons.collections4.Bag;
import org.apache.commons.collections4.bag.HashBag;
import org.apache.commons.collections4.bag.TreeBag;

/** * Bag 包允许重复 * 1.HashMap 无序 * 2.TreeMap 有序 * 统计单词的出现次数 */
public class Demo08 {
    public static void main(String[] args) {
        hashBag();
        treeBag();
        wordcount();//统计单词的出现次数 
    }

    //无序的包
    public static void hashBag()
    {
        System.out.println("=====无序的包========");
        Bag<String> bag = new HashBag<>();
        bag.add("a");
        bag.add("a",5);
        bag.remove("a",2);
        bag.add("b");
        bag.add("c");
        Iterator<String> it = bag.iterator();
        while(it.hasNext())
        {
            System.out.print(it.next()+" ");
        }
        System.out.println();
    }

    //有序的包
    public static void treeBag()
    {
        System.out.println("=====有序的包========");
        Bag<String> bag = new TreeBag<>();
        bag.add("a");
        bag.add("a",5);
        bag.remove("a",2);
        bag.add("b");
        bag.add("c");
        Iterator<String> it = bag.iterator();
        while(it.hasNext())
        {
            System.out.print(it.next()+" ");
        }
        System.out.println();
    }

    public static void wordcount(){
        String str = "this is a cat and that is a micewhere is the food";
        String[]  strArray  = str.split(" ");
        Bag<String> bag = new TreeBag<>();
        for(String temp:strArray)
        {
            bag.add(temp);
        }

        System.out.println("=====统计次数========");
        Set<String> keys = bag.uniqueSet();
        for(String letter:keys)
        {
            System.out.println(letter+"-->"+bag.getCount(letter));
        }
    }   
}

运行结果：

=====无序的包========
b c a a a a 
=====有序的包========
a a a a b c 
=====统计次数========
a-->2
and-->1
cat-->1
food-->1
is-->3
micewhere-->1
that-->1
the-->1
this-->1

原文链接：https://blog.csdn.net/scgaliguodong123_/article/details/45874503

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