java学习map集合训练

题目

1、手动输入一串无序的英文字母，输出每个字母的出现的个数

2、根据8月17日练习题，使用hashmap实现购物车功能

3、某中学刚结束期末考试，一班五名同学的成绩出来了，成绩包括语文、数学、英语、综合、体育、音乐，根据学生姓名查询该学生所有成绩。

4、已知一个 HashMap，User>集合， User 有 name（String）和 age（int）属性。请写一个方法实现对HashMap 的排序功能，该方法接收 HashMap，User>为形参，返回类型为 HashMap，User>，要求对 HashMap 中的 User 的age 倒序进行排序。排序时 key=value 键值对不得拆散。

5、实现省市区三级查询，例如吉林省———长春市———朝阳区，一个省有多个市，一个市有多个区，输入省名称，显示所有的市名称，每个市又显示出所有的区（最后做，不强制要求）

解答：

第一题：
package homework;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Map.Entry;
import java.util.Scanner;
import java.util.Set;
public class Test {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String s = sc.next();
        String[] mm = s.split("");
        
        HashMap map = new HashMap();
        for (int i = 1; i < mm.length; i++) {
            if (map.get(mm[i])!=null) {
                    map.put(mm[i],map.get(mm[i]) + 1);
                } else {
                    map.put(mm[i], 1);
                }
            }
        
        for (String d:map.keySet()) {
            System.out.println(d+"="+map.get(d));
        }
    }
}

第二题：
package homework;

import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map.Entry;
import java.util.Scanner;
import java.util.Set;

public class ShangCheng {

    public static void main(String[] args) {

        ArrayList list = liebiao();
        for (ShangP s : list) {
            System.out.println(s.toString());
        }
        System.out.println("**价格高于100的有**");
        for (ShangP n : list) {
            if (n.getPrice() > 100) {
                System.out.println(n);
            }
        }
        System.out.println("**产地是北京的有**");
        for (ShangP n : list) {
            if (n.getAddress().equals("北京")) {
                System.out.println(n);
            }
        }
        System.out.println("**排序**");
        Collections.sort(list);
        for (ShangP n : list) {
            System.out.println(n.toString());
        }
        System.out.println("**请抽奖**");
        chou();
        System.out.println("**请购物**");
        
        
        double sum = 0;
        HashMap str=new HashMap();
        while (true) {
            boolean isok=false;
            System.out.print("请输入购买物品");
            String name = new Scanner(System.in).next();
            System.out.print("请输入购买数量");
            int num = new Scanner(System.in).nextInt();
            for (ShangP l : list) {
                if (l.getName().equals(name)) {
                    gouwuche gg = new gouwuche(name, num, l.getPrice());
                    str.put(name, gg);
                    System.out.println("是否继续购买（是/结账）");
                    String s = new Scanner(System.in).next();
                    Set> entrySet = str.entrySet();
                    if (s.equals("结账")) {
                        for (Entry st:entrySet) {
                            sum+=(st.getValue().getPrice())*(st.getValue().getNum());
                            isok=true;
                        }

                    }

                    break;
                }

            }
            if(isok){
        System.out.println("您需要支付" + sum);
            }
        }

    }



    public static void chou() {
        ArrayList list = liebiao();
        int a = (int) (Math.random()*list.size());
        
        System.out.println("抽到了"+list.get(a));
        System.out.println();

    }

    public static ArrayList liebiao() {
        ArrayList list = new ArrayList();
        SW a1 = new SW("食物1", 12, "好", "大龙厂", "浙江", 9, 90);
        SW a2 = new SW("食物2", 12, "好", "大龙厂", "浙江", 9, 90);
        SW a3 = new SW("食物3", 12, "好", "大龙厂", "浙江", 9, 90);
        SW a4 = new SW("食物4", 12, "好", "大龙厂", "浙江", 9, 90);
        SW a5 = new SW("食物5", 12, "好", "大龙厂", "浙江", 9, 90);
        DQ b1 = new DQ("空调1", 10000, "好", "美的", "黑龙江", 220, 2500, 300);
        DQ b2 = new DQ("空调2", 10000, "好", "美的", "黑龙江", 220, 2500, 300);
        DQ b3 = new DQ("空调3", 10000, "好", "美的", "黑龙江", 220, 2500, 300);
        DQ b4 = new DQ("空调4", 10000, "好", "美的", "黑龙江", 220, 2500, 300);
        DQ b5 = new DQ("空调5", 10000, "好", "美的", "黑龙江", 220, 2500, 300);
        FZ c1 = new FZ("巴黎世家1", 1000, "优", "巴黎世家工厂", "广州", "涤纶", "棉麻", "布，水，线");
        FZ c2 = new FZ("巴黎世家2", 1000, "优", "巴黎世家工厂", "广州", "涤纶", "棉麻", "布，水，线");
        FZ c3 = new FZ("巴黎世家3", 1000, "优", "巴黎世家工厂", "广州", "涤纶", "棉麻", "布，水，线");
        FZ c4 = new FZ("巴黎世家4", 1000, "优", "巴黎世家工厂", "广州", "涤纶", "棉麻", "布，水，线");
        FZ c5 = new FZ("巴黎世家5", 1000, "优", "巴黎世家工厂", "北京", "涤纶", "棉麻", "布，水，线");
        WJ d1 = new WJ("泡泡机1", 200, "差", "江南皮革厂", "江苏", "皮革", "益智玩具", 3);
        WJ d2 = new WJ("泡泡机2", 200, "差", "江南皮革厂", "北京", "皮革", "益智玩具", 3);
        WJ d3 = new WJ("泡泡机3", 200, "差", "江南皮革厂", "江苏", "皮革", "益智玩具", 3);
        WJ d4 = new WJ("泡泡机4", 200, "差", "江南皮革厂", "江苏", "皮革", "益智玩具", 3);
        WJ d5 = new WJ("泡泡机5", 200, "差", "江南皮革厂", "江苏", "皮革", "益智玩具", 3);
        list.add(a1);
        list.add(a2);
        list.add(a3);
        list.add(a4);
        list.add(a5);
        list.add(b1);
        list.add(b2);
        list.add(b3);
        list.add(b4);
        list.add(b5);
        list.add(c1);
        list.add(c2);
        list.add(c3);
        list.add(c4);
        list.add(c5);
        list.add(d1);
        list.add(d2);
        list.add(d3);
        list.add(d4);
        list.add(d5);
        return list;
    }
}

第三题，package homework2;

public class Student {
    private double YW;
    private double SX;
    private double Y;
    private double ZH;
    private double TY;
    private double YY;
    public Student(double yW, double sX, double y, double zH, double tY, double yY) {
        super();
        YW = yW;
        SX = sX;
        Y = y;
        ZH = zH;
        TY = tY;
        YY = yY;
    }
    /**
     * @return the yW
     */
    public double getYW() {
        return YW;
    }
    /**
     * @param yW the yW to set
     */
    public void setYW(double yW) {
        YW = yW;
    }
    /**
     * @return the sX
     */
    public double getSX() {
        return SX;
    }
    /**
     * @param sX the sX to set
     */
    public void setSX(double sX) {
        SX = sX;
    }
    /**
     * @return the y
     */
    public double getY() {
        return Y;
    }
    /**
     * @param y the y to set
     */
    public void setY(double y) {
        Y = y;
    }
    /**
     * @return the zH
     */
    public double getZH() {
        return ZH;
    }
    /**
     * @param zH the zH to set
     */
    public void setZH(double zH) {
        ZH = zH;
    }
    /**
     * @return the tY
     */
    public double getTY() {
        return TY;
    }
    /**
     * @param tY the tY to set
     */
    public void setTY(double tY) {
        TY = tY;
    }
    /**
     * @return the yY
     */
    public double getYY() {
        return YY;
    }
    /**
     * @param yY the yY to set
     */
    public void setYY(double yY) {
        YY = yY;
    }
    /* (non-Javadoc)
     * @see java.lang.Object#toString()
     */
    @Override
    public String toString() {
        return "Student [YW=" + YW + ", SX=" + SX + ", Y=" + Y + ", ZH=" + ZH + ", TY=" + TY + ", YY=" + YY + "]";
    }
    
    
}
package homework2;

import java.util.HashMap;
import java.util.Map.Entry;
import java.util.Scanner;
import java.util.Set;

public class Test2 {

    public static void main(String[] args) {
        System.out.println(132);
        HashMap list=new HashMap();
        list.put("一号", new Student(90, 99, 90, 99, 90, 99));
        list.put("二号", new Student(90, 99, 90, 99, 90, 99));
        list.put("三号", new Student(90, 99, 90, 99, 90, 99));
        list.put("四号", new Student(90, 99, 90, 99, 90, 99));
        list.put("五号", new Student(90, 99, 90, 99, 90, 99));
        String name=new Scanner(System.in).next();
        Set> entrySet = list.entrySet();
        for(Entry ent:entrySet)
        {
            if(name.equals(ent.getKey()))
            System.out.println(ent);
        }
        
    }

}




第四题：
package homework4;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

public class User implements Comparable {
    private String name;
    private int age;

    public User(String name, int age) {
        super();
        this.name = name;
        this.age = age;
    }

    /**
     * @return the name
     */
    public String getName() {
        return name;
    }

    /**
     * @param name
     *            the name to set
     */
    public void setName(String name) {
        this.name = name;
    }

    /**
     * @return the age
     */
    public int getAge() {
        return age;
    }

    /**
     * @param age
     *            the age to set
     */
    public void setAge(int age) {
        this.age = age;
    }

    /*
     * (non-Javadoc)
     * 
     * @see java.lang.Object#toString()
     */
    @Override
    public String toString() {
        return "User [name=" + name + ", age=" + age + "]";
    }

    public User() {
        super();
    }

    public HashMap sortt(HashMap hash) {

        Set> entrySet = hash.entrySet();

        // 套一个List集合
        List> list = new ArrayList>(entrySet);

        Collections.sort(list,new Comparator>() {

            @Override
            public int compare(Entry o1, Entry o2) {
                return o2.getValue().age-o1.getValue().age;
            }
            
        });
        LinkedHashMap linkedHashMap = new LinkedHashMap();
        for(Entry entity : list){
            linkedHashMap.put(entity.getKey(), entity.getValue());
            System.out.println(entity.getKey());
        }
        return linkedHashMap;
    }

    private User getValue() {
        return null;
    }

    @Override
    public int compareTo(User o) {
        if (this.getAge() > o.getAge())
            return -1;
        else if (this.getAge() < o.getAge())
            return 1;
        else
            return 0;
    }

}

package homework4;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

public class Testuser {
public static void main(String[] args) {
    User u1=new User("王", 12);
    User u2=new User("张", 16);
    User u3=new User("孙", 10);
    
    HashMap hash=new HashMap<>();
    hash.put(1, u1);
    hash.put(2, u2);
    hash.put(3, u3);
    
    
    User u=new User();
    
    
    Set> entrySet = u.sortt(hash).entrySet();
    for(Entry d:entrySet)
    {
        System.out.println(d);
    }
}
    
//    public static void main(String[] args) {
//        LinkedHashMap map = new LinkedHashMap();
//        map.put("1","aaa");
//        map.put("3","bbb");
//        map.put("2","ccc");
//        map.put("5","ddd");
//        List> infoIds =new ArrayList>(map.entrySet());
//        //排序
//        Collections.sort(infoIds, new Comparator>() {
//            public int compare(Map.Entry o1, Map.Entry o2) {
//                String p1 =  o1.getKey();
//                String p2 = o2.getKey();;
//                return Integer.valueOf(p2)-Integer.valueOf(p1);//如果要升序， 改为return Integer.valueOf(p1)-Integer.valueOf(p2);
//            }
//        });
//       //转换成新map输出
//        LinkedHashMap newMap = new LinkedHashMap ();
//
//        for(Map.Entry entity : infoIds){
//            newMap.put(entity.getKey(), entity.getValue());
//            System.out.println(entity.getKey());
//        }
//    }
}

第五题：
package homework5;

public class City {
    private String name;

    /**
     * @return the name
     */
    public String getName() {
        return name;
    }

    /**
     * @param name the name to set
     */
    public void setName(String name) {
        this.name = name;
    }

    public City(String name) {
        super();
        this.name = name;
    }

    /* (non-Javadoc)
     * @see java.lang.Object#toString()
     */
    @Override
    public String toString() {
        return "City [name=" + name + "]";
    }
    
}
package homework5;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

public class Test {
    public static void main(String[] args) {
        //**注意map中元素不可重复**
        
        //区级list集合
        ArrayList li11=new ArrayList();
        ArrayList li12=new ArrayList();
        
        //市级对应区级，map集合
        HashMap> li21=new HashMap>();
        HashMap> li22=new HashMap>();
        
        //区级，list集合
        ArrayList>> li31=new ArrayList>>();
        
        //省级，map集合
        HashMap>>> list=new HashMap>>>();
        li11.add("船营区");
        li11.add("丰满区");
        li21.put("长春市",li11);
        li12.add("船营区");
        li12.add("丰满区");
        li22.put("吉林市",li12);
        li31.add(li21);
        li31.add(li22);
        list.put("吉林省", li31);
        Set>>>> entrySet = list.entrySet();
        for(Entry>>> d:entrySet)
        {
            System.out.println(d);
        }
        
        
    }
}