java编写读者类实现增删改查，充值和登录，编号流水自动增长以及按照身份等级进行借书折扣的代码

以下是一个简单的读者类实现，包括增加、删除、修改、查询、充值和登录功能，以及编号流水自动增长和按身份等级进行借书折扣的功能：

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

public class Reader {
    private static int nextId = 1;
    private int id;
    private String name;
    private String password;
    private double balance;
    private int level;

    private static List<Reader> readers = new ArrayList<>();

    public Reader(String name, String password, double balance, int level) {
        this.id = nextId++;
        this.name = name;
        this.password = password;
        this.balance = balance;
        this.level = level;
    }

    public int getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public String getPassword() {
        return password;
    }

    public double getBalance() {
        return balance;
    }

    public int getLevel() {
        return level;
    }

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

    public void setPassword(String password) {
        this.password = password;
    }

    public void setBalance(double balance) {
        this.balance = balance;
    }

    public void setLevel(int level) {
        this.level = level;
    }

    public static List<Reader> getReaders() {
        return readers;
    }

    public static void addReader(Reader reader) {
        readers.add(reader);
    }

    public static void removeReader(int id) {
        for (Reader reader : readers) {
            if (reader.getId() == id) {
                readers.remove(reader);
                break;
            }
        }
    }

    public static void modifyReader(int id, String name, String password, double balance, int level) {
        for (Reader reader : readers) {
            if (reader.getId() == id) {
                reader.setName(name);
                reader.setPassword(password);
                reader.setBalance(balance);
                reader.setLevel(level);
                break;
            }
        }
    }

    public static Reader findReader(int id) {
        for (Reader reader : readers) {
            if (reader.getId() == id) {
                return reader;
            }
        }
        return null;
    }

    public void recharge(double amount) {
        this.balance += amount;
    }

    public boolean login(String password) {
        return this.password.equals(password);
    }

    public double getDiscount() {
        switch (level) {
            case 1:
                return 1.0;
            case 2:
                return 0.9;
            case 3:
                return 0.8;
            default:
                return 1.0;
        }
    }
}

使用示例：

// 添加读者
Reader.addReader(new Reader("Tom", "123456", 100, 1));

// 删除读者
Reader.removeReader(1);

// 修改读者信息
Reader.modifyReader(2, "Jerry", "654321", 200, 2);

// 查询读者信息
Reader reader = Reader.findReader(2);

// 充值
reader.recharge(50);

// 登录
if (reader.login("654321")) {
    System.out.println("登录成功");
} else {
    System.out.println("登录失败");
}

// 获取折扣
double discount = reader.getDiscount();

注意，这只是一个简单的实现，实际应用中可能需要更加完善的设计和实现。