java/CAR/Car.java

package com.rental;

/**
 * 车辆管理系统的Car类，封装车辆属性和业务行为
 */
import java.util.Objects;
import java.util.concurrent.atomic.AtomicInteger;

public class Car {
    // 私有属性
    private final String licensePlate; // 车牌号不可变，加final
    private String brand;
    private String model;
    private double dailyRent;
    private boolean isRented;

    // 静态变量：统计车辆总数（线程安全）
    private static final AtomicInteger totalCars = new AtomicInteger(0);

    // 全参构造方法：车牌号、品牌、型号、日租金
    public Car(String licensePlate, String brand, String model, double dailyRent) {
        if (licensePlate == null || licensePlate.trim().isEmpty()) {
            throw new IllegalArgumentException("车牌号不能为空");
        }
        if (brand == null || brand.trim().isEmpty()) {
            throw new IllegalArgumentException("品牌不能为空");
        }
        if (model == null || model.trim().isEmpty()) {
            throw new IllegalArgumentException("型号不能为空");
        }
        this.licensePlate = licensePlate.trim();
        this.brand = brand.trim();
        this.model = model.trim();
        this.dailyRent = validateDailyRent(dailyRent);
        this.isRented = false;
        totalCars.incrementAndGet();
    }

    // 三参构造方法：调用全参构造，日租金默认300
    public Car(String licensePlate, String brand, String model) {
        this(licensePlate, brand, model, 300.0); // this()必须是构造方法第一行
    }

    // Getter：车牌号（仅get，无set）
    public String getLicensePlate() {
        return licensePlate;
    }

    // 品牌：get+set
    public String getBrand() {
        return brand;
    }
    public void setBrand(String brand) {
        this.brand = brand;
    }

    // 型号：get+set
    public String getModel() {
        return model;
    }
    public void setModel(String model) {
        this.model = model;
    }

    // 日租金：get+set（含合法性校验）
    public double getDailyRent() {
        return dailyRent;
    }
    public void setDailyRent(double dailyRent) {
        this.dailyRent = validateDailyRent(dailyRent);
    }

    // 私有方法：验证日租金合法性
    private double validateDailyRent(double dailyRent) {
        if (dailyRent > 0) {
            return dailyRent;
        } else {
            System.out.println("日租金必须大于0，使用默认值300元/天");
            return 300.0;
        }
    }

    // 租出状态：仅查询（isXXX命名规范），无set
    public boolean isRented() {
        return isRented;
    }

    // 静态方法：获取车辆总数
    public static int getTotalCars() {
        return totalCars.get();
    }

    // 业务方法：租车
    public boolean rentCar() {
        if (isRented) {
            System.out.println("车牌号【" + licensePlate + "】：车辆已租出，无法再次租用");
            return false;
        } else {
            isRented = true;
            System.out.println("车牌号【" + licensePlate + "】：租车成功，车辆已租出");
            return true;
        }
    }

    // 业务方法：还车
    public boolean returnCar() {
        if (!isRented) {
            System.out.println("车牌号【" + licensePlate + "】：车辆未被租用，无需归还");
            return false;
        } else {
            isRented = false;
            System.out.println("车牌号【" + licensePlate + "】：还车成功，车辆已归还");
            return true;
        }
    }

    // 业务方法：计算总租金（日租金×天数）
    public double calculateRent(int days) {
        if (days <= 0) {
            throw new IllegalArgumentException("租车天数必须大于0");
        }
        return dailyRent * days;
    }

    // 自定义方法：展示车辆完整信息（方便测试）
    public void displayInfo() {
        System.out.println("=====================");
        System.out.println("车牌号：" + licensePlate);
        System.out.println("品牌型号：" + brand + "-" + model);
        System.out.println("日租金：" + dailyRent + "元/天");
        System.out.println("车辆状态：" + (isRented ? "已租出" : "可租用"));
        System.out.println("=====================\n");
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Car car = (Car) o;
        return Objects.equals(licensePlate, car.licensePlate);
    }

    @Override
    public int hashCode() {
        return Objects.hash(licensePlate);
    }

    @Override
    public String toString() {
        return "Car{" +
                "licensePlate='" + licensePlate + '\'' +
                ", brand='" + brand + '\'' +
                ", model='" + model + '\'' +
                ", dailyRent=" + dailyRent +
                ", isRented=" + isRented +
                '}';
    }
}