case1： 集合、Random随机数、多态、封装

ShootOddPeople类 

package com.zz.examine.case1;

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

/**
 *
 */
public class ShootOddPerson {
    public static List<People> peoples = new ArrayList <>();
    public static void main(String args[]){
        //目标：完成幸存者案例
        /**
         * 1.由于每个囚犯是一个对象，
         * 并且我们需要每个囚犯的编号和 位置，
         * 所以我们需要将囚犯封装成对象.
         * 2.创建100个囚犯，依次站位，并为其赋值编号（1-200）的随机数，不能重复
         */
        //3.循环100次，创建100个囚犯，存入集合
        Random r = new Random();
        for(int i = 1;i <= 100; i++){
            while(true){
                int code = r.nextInt(200) + 1;
                //判断编号是否唯一
                if(exist(code)) {
                    People p = new People(code, i);
                    peoples.add(p);
                    break;//代表当前囚犯添加成功
                }
            }
        }
        System.out.println("囚犯站位" + peoples);

        //4.反复删除奇数位置处的人，知道剩余一个人为止
        //peoples = [p1,p2,p3,.....]
        while(peoples.size() > 1){
            //干掉奇数位置的人：逆向思维--留下偶数位置处的人
            List<People> tempPeoples = new ArrayList <>();
            for(int i = 1; i < peoples.size(); i+=2){
                People p = peoples.get(i);
                tempPeoples.add(p);
            }
            peoples = tempPeoples;
        }
        People luckPeople = peoples.get(0);
        System.out.println(luckPeople);
    }
    //判断编号是否存在
    public static boolean exist(int code){
        for(People people:peoples){
            if(people.getCode() == code)
                return false;//重复了，不能用
        }
        return true;
    }
}

 People类

package com.zz.examine.case1;

public class People {
    private int code;//编号
    private int location;//位置

    public People() {
    }

    public People(int code, int location) {
        this.code = code;
        this.location = location;
    }

    public int getCode() {
        return code;
    }

    public void setCode(int code) {
        this.code = code;
    }

    public int getLocation() {
        return location;
    }

    public void setLocation(int location) {
        this.location = location;
    }

    @Override
    public String toString() {
        return "People{" + "code=" + code + ", location=" + location + '}';
    }
}

case2：LocalDate ，Map集合，split方法分割，

Test类 

package com.zz.examine.case2;

import com.sun.javafx.image.IntPixelGetter;

import java.time.LocalDate;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class Test {
    public static void main(String args[]){
        //1.把数据拿到程序中
        String userStrs = "1001:张三:男:1998-02-23#1002:李四:女:1849-12-12#1003:王五:男:2000-12-12#1003:张三:女:2010-12-12";
        //2.定义一个用户类
        //3.提前定义一个List<User>集合用于存储用户集合
        List<User> users = new ArrayList <>();
        //4.把全部用户数据，用#分割
        String[] userStrArray = userStrs.split("#");
        for (String userStr : userStrArray) {
            //userStr = "1001:张三:男:1998-02-23"
            //5.创建一个用户对象，封装这个用户数据
            User user = new User();
            String[] userInfo = userStr.split(":");
            user.setId(Long.valueOf(userInfo[0]));
            user.setName(userInfo[1]);
            user.setGender(userInfo[2]);
            user.setBirthday(LocalDate.parse(userInfo[3]));
            //6.把这个用户存入到集合总
            users.add(user);
        }
        System.out.println(users);

        System.out.println("============业务二===========");
        //7.遍历List集合中的用户对象，统计相同名称出现的次数
        Map<String, Integer> result = new HashMap <>();
        for (User user : users) {
            String name = user.getName();
            if(result.containsKey(name)){
                result.put(name, result.get(name) + 1);
            }else{
                result.put(name, 1);
            }
        }
        //8.遍历Map集合
        result.forEach((k,v)->{
            System.out.println(k + ":" + v + "次");
        });
    }
}

User类 

package com.zz.examine.case2;

import java.time.LocalDate;

public class User {
    private Long id;
    private String name;
    private String gender;//性别
    private LocalDate birthday;//生日

    public User() {
    }

    public User(Long id, String name, String gender, LocalDate birthday) {
        this.id = id;
        this.gender = gender;
        this.birthday = birthday;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public LocalDate getBirthday() {
        return birthday;
    }

    public void setBirthday(LocalDate birthday) {
        this.birthday = birthday;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "User{" + "id=" + id + ", name='" + name + '\'' + ", gender='" + gender + '\'' + ", birthday=" + birthday + '}';
    }
}