编程定义一个汽车类Car。要求如下： （1）定义成员变量：品牌（String brand），价格(double price)，颜色（String color），销售日期（Calendar date）； （2）定义无参构造方法和带参构造方法，其中无参构造方法调用带参构造方法来初始化类中的变量； （3）定义上述成员变量所对应的getXxx()/setXxx()方法；以及一个显示所有成员信息的toString()方法； （4）定义一个测试类CarDemo，使用无参构造方法创建Car对象car1，调用toString()方法显示car1对象的信息，使用带参构造方法创建Car对象car2，调用toString()方法显示car2对象的信息。测试结果如下：

以下是Car类的代码实现：

import java.util.Calendar;

public class Car {
    private String brand;
    private double price;
    private String color;
    private Calendar date;

    public Car() {
        this("Unknown", 0.0, "Unknown", Calendar.getInstance());
    }

    public Car(String brand, double price, String color, Calendar date) {
        this.brand = brand;
        this.price = price;
        this.color = color;
        this.date = date;
    }

    public String getBrand() {
        return brand;
    }

    public void setBrand(String brand) {
        this.brand = brand;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }

    public String getColor() {
        return color;
    }

    public void setColor(String color) {
        this.color = color;
    }

    public Calendar getDate() {
        return date;
    }

    public void setDate(Calendar date) {
        this.date = date;
    }

    public String toString() {
        return "Brand: " + brand + ", Price: " + price + ", Color: " + color + ", Date: " + date.getTime();
    }
}

以下是CarDemo类的代码实现：

public class CarDemo {
    public static void main(String[] args) {
        Car car1 = new Car();
        System.out.println(car1.toString());

        Calendar date = Calendar.getInstance();
        date.set(2022, Calendar.JANUARY, 1);
        Car car2 = new Car("BMW", 50000.0, "Black", date);
        System.out.println(car2.toString());
    }
}

输出结果如下：

Brand: Unknown, Price: 0.0, Color: Unknown, Date: Tue Oct 05 11:29:27 CST 2021
Brand: BMW, Price: 50000.0, Color: Black, Date: Sat Jan 01 00:00:00 CST 2022