1.遍历HashMap

public class Mmap {
    public static void main(String []args){
        Map<Integer,String>map = new HashMap<>();
        map.put(0,"yzq");
        map.put(3,"yxc");
        map.put(2,"yxxx");
        map.put(1,"yxcv");
        System.out.println(map.toString());

        //获取键对应的值
        System.out.println(map.get(2));

        //是否包含某个键
        System.out.println(map.containsKey(5));

        //删除某个键-值
        map.remove(1);

        //遍历map
        for(Map.Entry<Integer,String>entry:map.entrySet()){
            System.out.println(entry.getKey()+" "+entry.getValue());
        }
    }

2.TreeMap,按键值排序

 //按照键升序--使用TreeMap
        Map<Integer,String>orderMap = new TreeMap<>(Collections.reverseOrder());
        orderMap.putAll(map);
        System.out.println(orderMap.toString());

3.练习1–统计字符串每个字符的个数

package bilibili.chapter16;

import java.util.*;

public class StrMap{
    public static void main(String[] args) {

        Map<String,Integer>strMap = new TreeMap<>();
        Scanner sc = new Scanner(System.in);
        String str = sc.next();
        char []chars = str.toCharArray();
        for(char c:chars){
            String key = c + "";
            if(!strMap.containsKey(key)){
                strMap.put(key,1);
            }else{
                Integer value = strMap.get(key);
                value ++;
                strMap.put(key,value);
            }

        }

        for(Map.Entry<String,Integer>entry: strMap.entrySet()){
            System.out.println(entry.getKey() + " "+entry.getValue());

        }

        Map<String,Integer>reserveMap = new TreeMap<>(Comparator.reverseOrder());
        reserveMap.putAll(strMap);
        System.out.println("反序后");
        for(Map.Entry<String,Integer>entry: reserveMap.entrySet()){
            System.out.println(entry.getKey() + " "+entry.getValue());

        }
    }

}

4.练习2–斗地主

package bilibili.chapter16;

import java.util.*;

public class JQKMap {
    public static void main(String[] args) {
        String []colors = "♠-♥-♣-♦".split("-");
        String []numbers = "2-3-4-5-6-7-8-9-10-J-Q-K-A".split("-");
        HashMap<Integer,String>pokers = new HashMap<>();
        ArrayList<Integer>list = new ArrayList<>();
        list.add(0);
        list.add(1);
        pokers.put(0,"大王");
        pokers.put(1,"小王");
        int key = 2;
        for(String number:numbers){
            for(String color:colors){
                String p = color + number;
                pokers.put(key,p);
                list.add(key);
                key++;
            }

        }
        System.out.println(pokers);


        Collections.shuffle(list);
        ArrayList<Integer>dipai = new ArrayList<>();
        ArrayList<Integer>p1 = new ArrayList<>();
        ArrayList<Integer>p2 = new ArrayList<>();
        ArrayList<Integer>p3 = new ArrayList<>();

        for(int i=0;i<list.size();i++){
            Integer poker = list.get(i);
            if(i>51){
                dipai.add(poker);
            }else if(i%3==0){
                p1.add(poker);
            }else if(i%3==1){
                p2.add(poker);
            }else {
                p3.add(poker);
            }


        }

        Collections.sort(dipai);
        Collections.sort(p1);
        Collections.sort(p2);
        Collections.sort(p3);

        look("底牌",dipai,pokers);
        look("第一个人",p1,pokers);
        look("第二个人",p2,pokers);
        look("第三个人",p3,pokers);

    }

    private static void look(String name,ArrayList<Integer> list,HashMap<Integer,String>map){
        System.out.println(name+"的牌：");
        for(Integer poker:list){
            System.out.print(map.get(poker)+" ");
        }
        System.out.println();
    }

}