每日要点

杂项

• 模板方法模式
  模板方法模式(GoF设计模式)
  使用了JAVA的继承机制，在抽象类中定义一个模板方法，该方法引用了若干个抽象方法（由子类实现）或具体方法（子类可以覆盖重写）
• 多态
  用同样类型的引用，调用相同的方法，做了不同的事情 - 多态

昨日作业讲解

• 1.设计一个绘图系统
  图形:中心点坐标、颜色
  算周长、面积、画图
  支持画矩形、圆、等边三角形
  图形类:

/**
 * 图形(抽象类)
 * @author Kygo
 *
 */
public abstract class Shape {
    protected int centerX;
    protected int centerY;
    protected Color color;
    
    /**
     * 构造器
     * @param centerX 中心点的横坐标
     * @param centerY 中心点的纵坐标
     * @param color 颜色
     */
    public Shape(int centerX, int centerY, Color color) {
        this.centerX = centerX;
        this.centerY = centerY;
        this.color = color;
    }

    /**
     * 计算周长
     * @return 周长
     */
    public abstract double perimeter();
    
    /**
     * 计算面积
     * @return 面积
     */
    public abstract double area();
    
    /**
     * 绘图
     * @param g 画笔(绘图的上下文环境)
     */
    public void draw(Graphics g) {
        g.setColor(color);
        g.drawString(String.format("周长: %.2f", perimeter()), centerX, centerY);
        g.drawString(String.format("面积: %.2f", area()), centerX, centerY + 20);
    }
}

圆类:

/**
 * 圆
 * @author Kygo
 *
 */
public class Circle extends Shape {
    private int radius;
    
    public Circle(int centerX, int centerY, Color color, int radius) {
        super(centerX, centerY, color);
        this.radius = radius;
    }

    @Override
    public double perimeter() {
        return 2 * Math.PI * radius;
    }

    @Override
    public double area() {
        return Math.PI * radius * radius;
    }

    @Override
    public void draw(Graphics g) {
        super.draw(g);
        g.drawOval(centerX - radius, centerY - radius, 2 * radius, 2 * radius);
    }
}

矩形类:

public class Rectangle extends Shape{
    private int width;
    private int height;
    
    public Rectangle(int centerX, int centerY, Color color, int width, int height) {
        super(centerX, centerY, color);
        this.width = width;
        this.height = height;
    }

    @Override
    public double perimeter() {
        return 2 * (width + height);
    }

    @Override
    public double area() {
        return width * height;
    }

    @Override
    public void draw(Graphics g) {
        super.draw(g);
        g.drawRect(centerX - width / 2, centerY - height / 2, width, height);
    }
}

等边三角形类:

public class EquilateralTriangle extends Shape {
    private int length;
    
    public EquilateralTriangle(int centerX, int centerY, Color color, int length) {
        super(centerX, centerY, color);
        this.length = length;
    }

    @Override
    public double perimeter() {
        return 3 * length;
    }

    @Override
    public double area() {
        //return Math.sqrt(3) / 4 * length * length;
/*      double half = perimeter() / 2.0;
        return Math.sqrt(half * Math.pow(half - length, 3));*/
        return length * length * Math.cos(Math.PI / 6) / 2;
    }

    @Override
    public void draw(Graphics g) {
        super.draw(g);
        int x1 =centerX;
        int y1 =(int) (centerY - length / 2.0 / Math.cos(Math.PI / 6));
        int x2 = centerX - length / 2;
        int y2 = (int) (centerY + Math.tan(Math.PI / 6) * length / 2.0);
        int x3 = centerX + length / 2;
        int y3 = y2;
        g.setColor(color);
        g.drawLine(x1, y1, x2, y2);
        g.drawLine(x2, y2, x3, y3);
        g.drawLine(x3, y3, x1, y1);
    }
}

绘图系统类:

//设计一个绘图系统
//图形:
//中心点坐标、颜色
//算周长、面积、画图
//支持画矩形、圆、等边三角形
@SuppressWarnings("serial")
public class ShapeFrame extends JFrame {
    private Shape circle = new Circle(200, 200, Color.red, 100);
    private Shape rectangle = new Rectangle(300, 300, Color.BLUE, 300, 100);
    private Shape triangle = new EquilateralTriangle(400, 400, Color.GREEN, 200);
    
    public ShapeFrame() {
        this.setTitle("绘图");
        this.setSize(800, 600);
        this.setResizable(false);
        this.setLocationRelativeTo(null);
        this.setDefaultCloseOperation(EXIT_ON_CLOSE);
    }
    
    @Override
    public void paint(Graphics g) {
        super.paint(g);
        circle.draw(g);
        rectangle.draw(g);
        triangle.draw(g);
    }
    
    public static void main(String[] args) {
        new ShapeFrame().setVisible(true);
    }
}

例子

• 1.汽车租车系统
  小汽车
  普通 商务
  400 600/1天
  货车
  < 10T 1200
  < 20T 2000
  (>=) 20T 2500
  系统 选择租的车型 具体租哪个车 算租了多少天车 花多少钱
  交通工具类:

public abstract class Vehicle {
    protected String brand;
    
    public Vehicle(String brand) {
        this.brand = brand;
    }
    
    public String getBrand() {
        return brand;
    }
    
    public abstract int rentPerDay();
    
    public int calcRent(int days) {
        return days * rentPerDay();
    }
}

小汽车类:

public class Car extends Vehicle {
    private boolean normal;
    
    public Car(String brand, boolean normal) {
        super(brand);
        this.normal = normal;
    }

    @Override
    public int rentPerDay() {
        return normal ? 400 : 600;
    }
}

货车类:

public class Truck extends Vehicle {
    private double load;

    public Truck(String brand, double load) {
        super(brand);
        this.load = load;
    }

    @Override
    public int rentPerDay() {
        if (load < 10) {
            return 1200;
        }
        else if (load < 20) {
            return 2000;
        }
        else {
            return 2500;
        }
    }
}

测试类:

        Vehicle v1 = new Car("别克", false);
        System.out.println(v1.calcRent(5));
        
        Vehicle v2 =  new Truck("东方", 25);
        System.out.println(v2.calcRent(5));

2.国际象棋棋盘

@SuppressWarnings("serial")
public class ChessFrame extends JFrame {
    private Image knightImage;
    private Image rookImage;
    
    public ChessFrame() {
        this.setTitle("国际象棋");
        this.setSize(800, 700);
        this.setResizable(false);
        this.setLocationRelativeTo(null);
        this.setDefaultCloseOperation(EXIT_ON_CLOSE);
        try {
            knightImage = ImageIO.read(this.getClass().getClassLoader().getResource("22.png"));
            rookImage = ImageIO.read(this.getClass().getClassLoader().getResource("21.png"));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    
    @Override
    public void paint(Graphics g) {
        super.paint(g);
        for (int i = 0; i < 8; i++) {
            for (int j = 0; j < 8; j++) {
                g.setColor((i + j) % 2 == 0 ? new Color(210, 220, 162) : new Color(179, 56, 89));
                g.fillRect(120 + j * 70, 80 + i * 70, 70, 70);
            } 
        }
        g.setColor(Color.RED);
        ((Graphics2D)g).setStroke(new BasicStroke(4));
        g.drawRect(115, 75, 570, 570);
        g.drawImage(knightImage, 190, 80, 70, 70, null);
        g.drawImage(rookImage, 120, 80, 70, 70, null);
    }
    
    public static void main(String[] args) {
        new ChessFrame().setVisible(true);
    }
}