不会写 请教问题 java

1. 创建一个Shape父类，

a) 该类有一个Point的类型的私有属性center，表示shape的中心点坐标

b) 二个成员方法：double getArea()获取图形的面积，默认返回值为0，double getPerimeter() 获取图形的周长，默认返回值为0

2. 将Circle类改为继承自Shape类，删除原有的圆心属性， Shape类的center属性作为圆心，在此基础上修改原有的求两个圆的关系的方法，使其能够正常执行。

a) 重写Shape的getArea和getPerimer方法，以计算圆的周长和面积

b) 重写圆的toString方法，使得该方法能够显示圆心坐标和圆的半径

c) 重写圆的equals方法，当两个圆的圆心坐标相同，并且半径相同就认为两个圆相等

d) 重写hashCode方法，确保当equals方法为true时，hashCode值相等

e) 给每个圆定义编号属性，表明该圆是生成的第几个

f) 定义一个属性MIN_RADIUS，表示半径的最小值0.5（不可修改），当给半径赋值时，如果值小于该最小值，则将半径设为该最小值。

3. 定义一个长方形Rectangle类，该类继承自Shape类，

a) 该类有两个私有属性：width（宽），heighth（高）

b) 创建一个无参的构造方法，该方法创建一个中心在原点，宽高都为1的长方形

c) 创建一个有参的构造方法，该方法创建一个指定宽高和中心点的长方形

d) 重写父类的getArea和getPerimeter方法，计算长方形的周长和面积

e) 重写toString方法，使得该方法能显示长方形的宽、高和中心点坐标

4. 定义一个三角形Triangle类，该类继承自Shape类，

a) 该类有三个私有属性：a,b,c表示三角形的三个边

b) 定义一个无参构造方法，该方法创建一个三角形，中心点在原点，a，b，c的值都为1

c) 定义一个有参的构造方法，该方法创建一个指定边长和中心点的三角形

d) 重写父类的getArea和getPerimeter方法，计算三角形的周长和面积

e) 重写toString方法，使得该方法能显示三角形的三边和中心点坐标

5. 定义一个测试类TestShape，在main方法中定义一个Shape 变量shape，分别创建圆、长方形和三角形对象赋值给shape变量，赋值后通过调用shape的getArea，getPerimeter和toString方法，验证是否能正确计算不同图形的面积和周长。

好的，以下是Java代码实现：

import java.awt.Point;

public class Shape {
    private Point center;

    public Shape(Point center) {
        this.center = center;
    }

    public double getArea() {
        return 0;
    }

    public double getPerimeter() {
        return 0;
    }
}

public class Circle extends Shape {
    private static final double MIN_RADIUS = 0.5;
    private static int count = 0;
    private int id;
    private double radius;

    public Circle(Point center, double radius) {
        super(center);
        this.radius = Math.max(radius, MIN_RADIUS);
        count++;
        id = count;
    }

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

    public double getPerimeter() {
        return 2 * Math.PI * radius;
    }

    @Override
    public String toString() {
        return "Circle " + id + ": center = " + center + ", radius = " + radius;
    }

    @Override
    public boolean equals(Object obj) {
        if (obj == this) {
            return true;
        }
        if (!(obj instanceof Circle)) {
            return false;
        }
        Circle other = (Circle) obj;
        return center.equals(other.center) && radius == other.radius;
    }

    @Override
    public int hashCode() {
        int result = 17;
        result = 31 * result + center.hashCode();
        result = 31 * result + Double.hashCode(radius);
        return result;
    }
}

public class Rectangle extends Shape {
    private double width;
    private double height;

    public Rectangle() {
        this(new Point(0, 0), 1, 1);
    }

    public Rectangle(Point center, double width, double height) {
        super(center);
        this.width = width;
        this.height = height;
    }

    public double getArea() {
        return width * height;
    }

    public double getPerimeter() {
        return 2 * (width + height);
    }

    @Override
    public String toString() {
        return "Rectangle: center = " + center + ", width = " + width + ", height = " + height;
    }
}

public class Triangle extends Shape {
    private double a;
    private double b;
    private double c;

    public Triangle() {
        this(new Point(0, 0), 1, 1, 1);
    }

    public Triangle(Point center, double a, double b, double c) {
        super(center);
        this.a = a;
        this.b = b;
        this.c = c;
    }

    public double getArea() {
        double p = (a + b + c) / 2;
        return Math.sqrt(p * (p - a) * (p - b) * (p - c));
    }

    public double getPerimeter() {
        return a + b + c;
    }

    @Override
    public String toString() {
        return "Triangle: center = " + center + ", a = " + a + ", b = " + b + ", c = " + c;
    }
}

public class TestShape {
    public static void main(String[] args) {
        Shape shape;

        shape = new Circle(new Point(0, 0), 2);
        System.out.println(shape.toString());
        System.out.println("Area: " + shape.getArea());
        System.out.println("Perimeter: " + shape.getPerimeter());

        shape = new Rectangle(new Point(0, 0), 2, 3);
        System.out.println(shape.toString());
        System.out.println("Area: " + shape.getArea());
        System.out.println("Perimeter: " + shape.getPerimeter());

        shape = new Triangle(new Point(0, 0), 3, 4, 5);
        System.out.println(shape.toString());
        System.out.println("Area: " + shape.getArea());
        System.out.println("Perimeter: " + shape.getPerimeter());
    }
}

以下是Java代码实现（续）：

public class Circle extends Shape {
    private static final double MIN_RADIUS = 0.5;
    private static int count = 0;
    private int id;
    private double radius;

    public Circle(Point center, double radius) {
        super(center);
        this.radius = Math.max(radius, MIN_RADIUS);
        count++;
        id = count;
    }

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

    public double getPerimeter() {
        return 2 * Math.PI * radius;
    }

    @Override
    public String toString() {
        return "Circle " + id + ": center = " + center + ", radius = " + radius;
    }

    @Override
    public boolean equals(Object obj) {
        if (obj == this) {
            return true;
        }
        if (!(obj instanceof Circle)) {
            return false;
        }
        Circle other = (Circle) obj;
        return center.equals(other.center) && radius == other.radius;
    }

    @Override
    public int hashCode() {
        int result = 17;
        result = 31 * result + center.hashCode();
        result = 31 * result + Double.hashCode(radius);
        return result;
    }
}

public class Rectangle extends Shape {
    private double width;
    private double height;

    public Rectangle() {
        this(new Point(0, 0), 1, 1);
    }

    public Rectangle(Point center, double width, double height) {
        super(center);
        this.width = width;
        this.height = height;
    }

    public double getArea() {
        return width * height;
    }

    public double getPerimeter() {
        return 2 * (width + height);
    }

    @Override
    public String toString() {
        return "Rectangle: center = " + center + ", width = " + width + ", height = " + height;
    }
}

public class Triangle extends Shape {
    private double a;
    private double b;
    private double c;

    public Triangle() {
        this(new Point(0, 0), 1, 1, 1);
    }

    public Triangle(Point center, double a, double b, double c) {
        super(center);
        this.a = a;
        this.b = b;
        this.c = c;
    }

    public double getArea() {
        double p = (a + b + c) / 2;
        return Math.sqrt(p * (p - a) * (p - b) * (p - c));
    }

    public double getPerimeter() {
        return a + b + c;
    }

    @Override
    public String toString() {
        return "Triangle: center = " + center + ", a = " + a + ", b = " + b + ", c = " + c;
    }
}

public class TestShape {
    public static void main(String[] args) {
        Shape shape;

        shape = new Circle(new Point(0, 0), 2);
        System.out.println(shape.toString());
        System.out.println("Area: " + shape.getArea());
        System.out.println("Perimeter: " + shape.getPerimeter());

        shape = new Rectangle(new Point(0, 0), 2, 3);
        System.out.println(shape.toString());
        System.out.println("Area: " + shape.getArea());
        System.out.println("Perimeter: " + shape.getPerimeter());

        shape = new Triangle(new Point(0, 0), 3, 4, 5);
        System.out.println(shape.toString());
        System.out.println("Area: " + shape.getArea());
        System.out.println("Perimeter: " + shape.getPerimeter());
    }
}

可以参考:

public class Shape {

private int center;

private  double area=0;

private double perimeter=0;

public double getArea(){
return this.area;
}

public double getPerimeter(){

return this.perimeter;
}

}