HashMap的操作和应用

2019-02-18  本文已影响0人  黄同学2019

day18笔记【HashMap的操作和应用】

1_集合框架(Map集合概述和特点)

2_集合框架(Map集合的功能概述)

3_集合框架(Map集合的遍历之键找值)

4_集合框架(Map集合的遍历之键值对对象找键和值)

C:源码分析

5_集合框架(HashMap集合键是Student值是String的案例)

6_集合框架(LinkedHashMap的概述和使用)

7_集合框架(TreeMap集合键是Student值是String的案例)

8_集合框架(统计字符串中每个字符出现的次数)

        String str = "aaaabbbcccccccccc";
        char[] arr = str.toCharArray();                     //将字符串转换成字符数组
        HashMap<Character, Integer> hm = new HashMap<>();   //创建双列集合存储键和值
        for(char c : arr) {                                 //遍历字符数组
            /*if(!hm.containsKey(c)) {                      //如果不包含这个键
                hm.put(c, 1);                               //就将键和值为1添加
            }else {                                         //如果包含这个键
                    hm.put(c, hm.get(c) + 1);                   //就将键和值再加1添加进来
                }
  
            //hm.put(c, !hm.containsKey(c) ? 1 : hm.get(c) + 1);
            Integer i = !hm.containsKey(c) ? hm.put(c, 1) : hm.put(c, hm.get(c) + 1);
                    }
        
        for (Character key : hm.keySet()) {                 //遍历双列集合
            System.out.println(key + "=" + hm.get(key));
        }

9_集合框架(集合嵌套之HashMap嵌套HashMap)

10_集合框架(HashMap和Hashtable的区别)

11_集合框架(Collections工具类的概述和常见方法讲解)

12_集合框架(模拟斗地主洗牌和发牌)

        //买一副扑克
        String[] num = {"A","2","3","4","5","6","7","8","9","10","J","Q","K"};
        String[] color = {"方片","梅花","红桃","黑桃"};
        ArrayList<String> poker = new ArrayList<>();
            
        for(String s1 : color) {
            for(String s2 : num) {
                poker.add(s1.concat(s2));
            }
        }
        
        poker.add("小王");
        poker.add("大王");
        //洗牌
        Collections.shuffle(poker);
        //发牌
        ArrayList<String> gaojin = new ArrayList<>();
        ArrayList<String> longwu = new ArrayList<>();
        ArrayList<String> me = new ArrayList<>();
        ArrayList<String> dipai = new ArrayList<>();
        
        for(int i = 0; i < poker.size(); i++) {
            if(i >= poker.size() - 3) {
                dipai.add(poker.get(i));
            }else if(i % 3 == 0) {
                gaojin.add(poker.get(i));
            }else if(i % 3 == 1) {
                longwu.add(poker.get(i));
            }else {
                me.add(poker.get(i));
            }
        }
        
        //看牌
        
        System.out.println(gaojin);
        System.out.println(longwu);
        System.out.println(me);
        System.out.println(dipai);

13_集合框架(模拟斗地主洗牌和发牌并对牌进行排序的原理图解)

14_集合框架(模拟斗地主洗牌和发牌并对牌进行排序的代码实现)

    ​       //买一副牌
    ​           String[] num = {"3","4","5","6","7","8","9","10","J","Q","K","A","2"};
    ​           String[] color = {"方片","梅花","红桃","黑桃"};
    ​           HashMap<Integer, String> hm = new HashMap<>();          //存储索引和扑克牌
    ​           ArrayList<Integer> list = new ArrayList<>();            //存储索引
    ​           int index = 0;                                          //索引的开始值
    ​           for(String s1 : num) {
    ​               for(String s2 : color) {
    ​                   hm.put(index, s2.concat(s1));               //将索引和扑克牌添加到HashMap中
    ​                   list.add(index);                            //将索引添加到ArrayList集合中
    ​                   index++;
    ​               }
    ​           }
    ​           hm.put(index, "小王");
    ​           list.add(index);
    ​           index++;
    ​           hm.put(index, "大王");
    ​           list.add(index);
    ​           //洗牌
    ​           Collections.shuffle(list);
    ​           //发牌
    ​           TreeSet<Integer> gaojin = new TreeSet<>();
    ​           TreeSet<Integer> longwu = new TreeSet<>();
    ​           TreeSet<Integer> me = new TreeSet<>();
    ​           TreeSet<Integer> dipai = new TreeSet<>();
    ​       for(int i = 0; i < list.size(); i++) {
    ​           if(i >= list.size() - 3) {
    ​               dipai.add(list.get(i));                         //将list集合中的索引添加到TreeSet集合中会自动排序
    ​           }else if(i % 3 == 0) {
    ​               gaojin.add(list.get(i));
    ​           }else if(i % 3 == 1) {
    ​               longwu.add(list.get(i));
    ​           }else {
    ​               me.add(list.get(i));
    ​           }
    ​       }
    ​       
            //看牌
            lookPoker("高进", gaojin, hm);
            lookPoker("龙五", longwu, hm);
            lookPoker("冯佳", me, hm);
            lookPoker("底牌", dipai, hm);
            
        }
        public static void lookPoker(String name,TreeSet<Integer> ts,HashMap<Integer, String> hm) {
            System.out.print(name + "的牌是:");
            for (Integer index : ts) {
                System.out.print(hm.get(index) + " ");
            }
            
            System.out.println();
        }

15_集合框架(泛型固定下边界)

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