Java学习笔记（十二）

我会带着你远行 2023-09-30 08:04 34阅读 0赞

**目录**

一：Map

二：Collentions

三：java实现斗地主

--------------------

## 一：Map ##

**1.1 Map集合概述和使用：**

Map集合概述

*  Interface Map<K,V> K:键的使用 ； V:值的使用
 *  将键映射到值的对象； 不能包含重复的键；每个键可以映射到最多一个值
 *  举例：学生的学号和姓名

itheima001 小花

itheima002 小刚

itheima003 小雨

创建Map集合的对象

*  多态的方式
 *  具体的实现类HashMap

public class Main {
        public static void main(String[] args) {
            //创建集合对象
            Map<String, String> map=new HashMap<>();
    
            //V put(k key,V value)将指定的值与该映射中的指定键相关联
            map.put("itheima01","小周");
            map.put("itheima02","小王");
            map.put("itheima03","小雨");
            map.put("itheima03","小白");//小雨会被小白覆盖掉
    
    
            //输出集合对象
            System.out.println(map);//{itheima01=小周, itheima02=小王, itheima03=小白}
        }
    }

**1.2 Map集合的基本功能：**

**![watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBASmlhWGluZ05hc2hpc2h1YQ_size_13_color_FFFFFF_t_70_g_se_x_16][]**

**1.3 Map集合的获取功能：**

**![watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBASmlhWGluZ05hc2hpc2h1YQ_size_14_color_FFFFFF_t_70_g_se_x_16][]**

--------------------

public class Main {
        public static void main(String[] args) {
            //创建集合对象
            Map<String, String> map=new HashMap<>();
    
            //添加元素
            map.put("张无忌","赵敏");
            map.put("郭靖","黄蓉");
            map.put("杨过","小龙女");
    
            //V get(Object key):根据键获取值
            System.out.println(map.get("张无忌"));//赵敏
            System.out.println(map.get("张三丰"));//null
    
            //Set<K> keySet():获取所有键的集合
            Set<String> keySet=map.keySet();
            for(String key:keySet){
                System.out.println(key);//杨过 郭靖 张无忌
            }
    
            //Collection<V> values():获取所有值的集合
            Collection<String> values=map.values();
            for(String value:values){
                System.out.println(value);//小龙女  黄蓉  赵敏
            }
        }
    }

**1.4 Map集合的遍历（方式一）：**

![watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBASmlhWGluZ05hc2hpc2h1YQ_size_11_color_FFFFFF_t_70_g_se_x_16][]

public class Main {
        public static void main(String[] args) {
            //创建集合对象
            Map<String, String> map=new HashMap<>();
    
            //添加元素
            map.put("张无忌","赵敏");
            map.put("郭靖","黄蓉");
            map.put("杨过","小龙女");
            //获取所有键的集合，用keySet（）方法实现
            Set<String> keySet=map.keySet();
            //遍历键的集合，获取到每一个键，用增强for实现
            for (String key : keySet) {//快捷键：集合名.iter，可以实现for循环
    
                //根据键找到对应的值
                String value=map.get(key);
                System.out.println(key+","+value);
            }
        }
    }

**1.5 Map集合的遍历（方式2）**

**![watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBASmlhWGluZ05hc2hpc2h1YQ_size_11_color_FFFFFF_t_70_g_se_x_16 1][]**

public class Main {
        public static void main(String[] args) {
            //创建集合对象
            Map<String, String> map=new HashMap<>();
    
            //添加元素
            map.put("张无忌","赵敏");
            map.put("郭靖","黄蓉");
            map.put("杨过","小龙女");
            //获取所有键的集合，用keySet（）方法实现
            Set<Map.Entry<String, String>> entrySet=map.entrySet();
            //遍历键值对对象的集合，的到每一个键值对对象
            for(Map.Entry<String, String> me:entrySet){
                //根据键值对对象获取键和值
                String key=me.getKey();
                String value=me.getValue();
                System.out.println(key+","+value);
            }
        }
    }

**案例1：HashMap集合存储学生对象并遍历**

**![watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBASmlhWGluZ05hc2hpc2h1YQ_size_17_color_FFFFFF_t_70_g_se_x_16][]**

import java.util.*;
    public class Main {
        public static void main(String[] args) {
           //创建集合对象
            Map<student,String> map=new HashMap<>();
    
            //定义学生类对象
            student s1=new student("林青霞",18);
            student s2=new student("张曼玉",19);
            student s3=new student("王祖贤",20);
            student s4=new student("王祖贤",20);
            //添加元素
            map.put(s1,"西安");
            map.put(s2,"武汉");
            map.put(s3,"郑州");
            map.put(s4,"北京");//郑州被北京覆盖了
    
            //遍历集合
            Set<student> keySet=map.keySet();
            for(student s:keySet){
                String value=map.get(s);
                System.out.println(s.getName()+","+s.getAge()+","+value);
            }
        }
    }
    class student{
        private String name;
        private int age;
    
        public student() {
        }
    
        public student(String name, int age) {
            this.name = name;
            this.age = age;
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public int getAge() {
            return age;
        }
    
        public void setAge(int age) {
            this.age = age;
        }
    
        @Override
        public boolean equals(Object o) {
            if (this == o) return true;
            if (o == null || getClass() != o.getClass()) return false;
    
            student student = (student) o;
    
            if (age != student.age) return false;
            return name != null ? name.equals(student.name) : student.name == null;
        }
    
        @Override
        public int hashCode() {
            int result = name != null ? name.hashCode() : 0;
            result = 31 * result + age;
            return result;
        }
    }

**案例2：集合嵌套之ArrayList嵌套HashSet**

**![watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBASmlhWGluZ05hc2hpc2h1YQ_size_17_color_FFFFFF_t_70_g_se_x_16 1][]**

--------------------

import java.util.*;
    public class Main {
        public static void main(String[] args) {
            //创建ArrayList集合
            ArrayList<HashMap<String, String>> array = new ArrayList<>();
    
            //创建HashMap集合，并添加键值对元素
            HashMap<String, String> hashMap1 = new HashMap<>();
            hashMap1.put("孙策", "大乔");
            hashMap1.put("周瑜", "小乔");
            HashMap<String, String> hashMap2 = new HashMap<>();
            hashMap2.put("郭靖", "黄蓉");
            hashMap2.put("杨过", "小龙女");
            HashMap<String, String> hashMap3 = new HashMap<>();
            hashMap3.put("令狐冲", "任盈盈");
            hashMap3.put("林平之", "岳灵珊");
            //把hashMap作为元素添加到ArrayList集合
            array.add(hashMap1);
            array.add(hashMap2);
            array.add(hashMap3);
    
            //遍历ArrayList集合
            for (HashMap<String, String> hm : array) {
                Set<String> keySet = hm.keySet();
                for (String key : keySet) {
                    String value = hm.get(key);
                    System.out.println(key + "," + value);
                }
            }
    
        }
    }

**案例3：集合嵌套之HashSett嵌套ArrayList：**

**![watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBASmlhWGluZ05hc2hpc2h1YQ_size_15_color_FFFFFF_t_70_g_se_x_16][]**

--------------------

import java.util.*;
    public class Main {
        public static void main(String[] args) {
            //创建HashSet集合
          Map<String,ArrayList<String>> hashmap=new HashMap<>();
          //创建ArrayList集合
            ArrayList<String> array1=new ArrayList<>();
            array1.add("诸葛亮");
            array1.add("赵云");
            ArrayList<String> array2=new ArrayList<>();
            array2.add("唐僧");
            array2.add("孙悟空");
            ArrayList<String> array3=new ArrayList<>();
            array3.add("武松");
            array3.add("鲁智深");
            hashmap.put("sgyy",array1);
            hashmap.put("xyj",array2);
            hashmap.put("shz",array3);
            //遍历HashSet集合
            Set<String> keyset=hashmap.keySet();
            for(String s:keyset){
                System.out.println(s);
                ArrayList<String> values=hashmap.get(s);
                for(String value:values){
                    System.out.println("\t"+value);
                }
            }
    
    
    
        }
    }

**案例4：统计字符串中每个字符出现的次数：**

**![watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBASmlhWGluZ05hc2hpc2h1YQ_size_16_color_FFFFFF_t_70_g_se_x_16][]**

--------------------

import java.util.*;
    public class Main {
        public static void main(String[] args) {
            Scanner sc=new Scanner(System.in);
            System.out.println("请输入一段字符串：");
            String s=sc.nextLine();
            TreeMap<Character,Integer> tm=new TreeMap<>();
            for(int i=0;i<s.length();i++){
                char key=s.charAt(i);
                Integer value=tm.get(key);
                if(value==null){
                    tm.put(key,1);
                }else{
                    value++;
                    tm.put(key,value);
                }
            }
            StringBuilder sb=new StringBuilder();
             Set<Character> keymap = tm.keySet();
            for(Character c:keymap){
                Integer value=tm.get(c);
                sb.append(c).append("(").append(value).append(")");
            }
            System.out.println(sb.toString());
        }
    }

## 二：Collentions ##

**2.1 Collentions概述和使用**

是针对集合操作的工具类

Collentions类的常用方法

*  public static <T extends Comparable<? super T>> void sort(List<T>list):将指定的列表按升序排序。
 *  public static void reverse（List<?>list）:反转指定列表中元素的顺序。
 *  public static void shuffle（List<?>list）:使用默认的随机源随机排列指定的列表。

import java.util.*;
    public class Main {
        public static void main(String[] args) {
           //创建集合对象
            List<Integer> list=new ArrayList<Integer>();
    
            //添加集合
            list.add(30);
            list.add(20);
            list.add(50);
            list.add(10);
            list.add(40);
            Collections.sort(list);//升序
            Collections.reverse(list);//反转
            Collections.shuffle(list);//使用默认的随机源随机排列指定的列表
            System.out.println(list);
        }
    }

**案例：ArrayList存储学生对象并排序**

![watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBASmlhWGluZ05hc2hpc2h1YQ_size_11_color_FFFFFF_t_70_g_se_x_16 2][]

--------------------

import java.util.*;
    public class Main {
        public static void main(String[] args) {
            //创建集合对象
            ArrayList<student> array=new ArrayList<>();
            //定义学生类
            student s1=new student("lingqingxia",32);
            student s2=new student("zhangmanyu",35);
            student s3=new student("wangzuxian",33);
            student s4=new student("liuyan",33);
            student s5=new student("liuyan",33);
            //添加元素
            array.add(s1);
            array.add(s2);
            array.add(s3);
            array.add(s4);
            array.add(s5);
            //使用Collentions对ArrayList集合排序
            //sort（List<T> list,Comparator<? super T> c）
            Collections.sort(array, new Comparator<student>() {
                @Override
                public int compare(student s1,student s2) {
                    int num= s1.getAge()- s2.getAge();
                    int num1=num==0?s1.getName().compareTo(s2.getName()):num;
                    return num1;
                }
            });
            //遍历集合
            for(student s:array){
                System.out.println(s.getName()+","+s.getAge());
            }
    
        }
    }
    class student{
        private String name;
        private int age;
    
        public student() {
        }
    
        public student(String name, int age) {
            this.name = name;
            this.age = age;
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public int getAge() {
            return age;
        }
    
        public void setAge(int age) {
            this.age = age;
        }
    }

## **三：java实现斗地主** ##

**![watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBASmlhWGluZ05hc2hpc2h1YQ_size_13_color_FFFFFF_t_70_g_se_x_16 1][]**

import java.util.*;
    
    public class Main {
        //定义方法看牌
        public static void lookPoker(String name,TreeSet<Integer> ts,Map<Integer,String> hashMap){
            System.out.print(name+"的牌是：");
            for(Integer i:ts){
                String value=hashMap.get(i);
                System.out.print(value+" ");
            }
            System.out.println();
        }
        public static void main(String[] args) {
            //创建HashMap，键是编号，值是牌
            Map<Integer, String> hashMap = new HashMap<>();
    
            //创建ArrayList，存储编号
            ArrayList<Integer> array = new ArrayList<>();
    
            //创建花色数组和点数数组
            String[] pokerColors = {"◆", "♣", "♠", "♥"};
            String[] pokerPoints = {"3", "4", "5", "6", "7", "8", "9", "10", "J", "Q", "K", "A", "2"};
    
            //从0开始往HashMap里面存储编号，并存储对应的牌。同时往ArrayList里面存储编号
            int index = 0;
            for (String point : pokerPoints) {
                for (String color : pokerColors) {
                    hashMap.put(index, color + point);
                    array.add(index);
                    index++;
                }
            }
    
            //将大王和小王也存入牌盒中
            hashMap.put(index, "小王");
            array.add(index);
            index++;
            hashMap.put(index, "大王");
            array.add(index);
    
            //洗牌
            Collections.shuffle(array);
    
            //创建三个玩家对象以及三张底牌集合
            TreeSet<Integer> farmer1=new TreeSet<>();
            TreeSet<Integer> farmer2=new TreeSet<>();
            TreeSet<Integer> farmer3=new TreeSet<>();
            TreeSet<Integer> dpPokers=new TreeSet<>();
            
            //发牌
            for(int i=0;i<array.size();i++){
                int x=array.get(i);
                if(i>=array.size()-3){
                    dpPokers.add(x);
                }else if(i%3==0){
                    farmer1.add(x);
                }else if(i%3==1){
                    farmer2.add(x);
                }else if(i%3==2){
                    farmer3.add(x);
                }
            }
    
            //看牌
            lookPoker("农民一号",farmer1,hashMap);
            lookPoker("农民二号",farmer2,hashMap);
            lookPoker("农民三号",farmer3,hashMap);
            lookPoker("底牌",dpPokers,hashMap);
        }
    }

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