BLOG-2

考试分析：个人感觉本次考试难度偏简单，也无需注意些什么，只要仔细读题问题应该都不大；

1.创建一个圆形类（Circle），私有属性为圆的半径，从控制台输入圆的半径，输出圆的面积

输入格式:

输入圆的半径，取值范围为(0,+∞)，输入数据非法，则程序输出Wrong Format，注意：只考虑从控制台输入数值的情况

输出格式:

输出圆的面积（保留两位小数，可以使用String.format(“%.2f”,输出数值）控制精度）

import java.util.Scanner;

public class Main {
    private double radius;

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        double radius = scanner.nextDouble();

        Main circle = new Main();
        circle.setRadius(radius);

        double area = circle.calculateArea();

        if (area == -1) {
            System.out.println("Wrong Format");
        } else {
            System.out.println(String.format("%.2f", area));
        }
    }

    public void setRadius(double radius) {
        if (radius > 0) {
            this.radius = radius;
        } else {
            this.radius = -1;
        }
    }

    public double calculateArea() {
        if (radius == -1) {
            return -1;
        } else {
            return Math.PI * radius * radius;
        }
    }
}

2.设计一个矩形类，其属性由矩形左上角坐标点（x1，y1）及右下角坐标点（x2，y2）组成，其中，坐标点属性包括该坐标点的X轴及Y轴的坐标值（实型数），求得该矩形的面积。类设计如下图：

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        double x1 = scanner.nextDouble();
        double y1 = scanner.nextDouble();

        double x2 = scanner.nextDouble();
        double y2 = scanner.nextDouble();

        double area = calculateRectangleArea(x1, y1, x2, y2);

        System.out.println( String.format("%.2f", area));
    }

    public static double calculateRectangleArea(double x1, double y1, double x2, double y2) {
        double width = Math.abs(x2 - x1);
        double height = Math.abs(y2 - y1);

        return width * height;
    }
}

3.

将测验1与测验2的类设计进行合并设计，抽象出Shape父类（抽象类），Circle及Rectangle作为子类，类图如下所示：

其中，printArea(Shape shape)方法为定义在Main类中的静态方法，体现程序设计的多态性。

输入格式:

输入类型选择（1或2，不考虑无效输入）
对应图形的参数（圆或矩形）

输出格式:

图形的面积（保留两位小数）

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        int shapeType = scanner.nextInt();

        double area = 0.0;

        if (shapeType == 1) {
            double radius = scanner.nextDouble();
            if(radius<=0){
            System.out.println("Wrong Format");
            return;
        }
            area = calculateCircleArea(radius);
        } else if (shapeType == 2) {
        double x1 = scanner.nextDouble();
        double y1 = scanner.nextDouble();

        double x2 = scanner.nextDouble();
        double y2 = scanner.nextDouble();
            double length = Math.abs(x1-x2);
            double width = Math.abs(y1-y2);
            area = calculateRectangleArea(length, width);
        } else {
            System.out.println("Wrong Format");
            return;
        }

        System.out.println(String.format("%.2f", area));
    }

    public static double calculateCircleArea(double radius) {
        return Math.PI * radius * radius;
    }

    public static double calculateRectangleArea(double length, double width) {
        return length * width;
    }
}

4.

在测验3的题目基础上，重构类设计，实现列表内图形的排序功能（按照图形的面积进行排序）。

输入图形类型（1:圆形；2：矩形；0：结束输入）

输入图形所需参数

输出格式:

按升序排序输出列表中各图形的面积（保留两位小数），各图形面积之间用空格分隔。、

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        List<Double> areas = new ArrayList<>();

        int shapeType;

        do {


            shapeType = scanner.nextInt();

            if (shapeType == 1) {
                double radius = scanner.nextDouble();
            if(radius<=0){
            System.out.println("Wrong Format");
            return;
        }
                double area = calculateCircleArea(radius);
                areas.add(area);
            } else if (shapeType == 2) {
            double x1 = scanner.nextDouble();
            double y1 = scanner.nextDouble();
            double x2 = scanner.nextDouble();
            double y2 = scanner.nextDouble();
            double length = Math.abs(x1-x2);
            double width = Math.abs(y1-y2);
                double area = calculateRectangleArea(length, width);
                areas.add(area);
            } else if (shapeType != 0) {
                System.out.println("Wrong Format");
            }
        } while (shapeType != 0);

        Collections.sort(areas);

        for (double area : areas) {
            System.out.print(String.format("%.2f", area) + " ");
        }
    }

    public static double calculateCircleArea(double radius) {
        return Math.PI * radius * radius;
    }

    public static double calculateRectangleArea(double length, double width) {
        return length * width;
    }
}