我来写一下吧：
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abstract class Shape{
private double c;
private double s;
public abstract void girth();
public abstract void area();
public void setGirth(double c){
this.c = c;
}
public void setArea(double s){
this.s = s;
}
public double getGirth(){
return c;
}
public double getArea(){
return s;
}
public void outInfo(){}
}
class Circle extends Shape{
private static final double PI = 3.1415926;
private double r;
//定义一个构造函数
public Circle(double r){
this.r = r;
}
//重写抽象方法
public void girth() {
double a =2*PI*r;
super.setGirth(a);
}
public void area() {
double b =PI*r*r;
super.setArea(b);
}
public void outInfo() {
this.girth();
this.area();
System.out.println("所求圆形周长为："+super.getGirth());
System.out.println("所求圆形面积为："+super.getArea());
}
}
class Rectangle extends Shape{
private double height;
private double width;
//定义一个构造函数
public Rectangle(double height,double width){
this.height = height;
this.width = width;
}
//重写抽象方法
public void girth() {
double a =2*(height+width);
super.setGirth(a);
}
public void area() {
double b =(height*width);
super.setArea(b);
}
public void outInfo() {
this.girth();
this.area();
System.out.println("所求矩形周长为："+super.getGirth());
System.out.println("所求矩形面积为："+super.getArea());
}
}
class Triangle extends Shape{
private double lengthA;
private double lengthB;
private double lengthC;
//定义一个构造函数
public Triangle(double lengthA,double lengthB,double lengthC){
this.lengthA = lengthA;
this.lengthB = lengthB;
this.lengthC = lengthC;
}
//重写抽象方法
public void girth() {
double a =(lengthA+lengthB+lengthC);
super.setGirth(a);
}
public void area() {
if((lengthA+lengthB lengthC) || (lengthA + lengthC lengthB) || (lengthB+lengthC lengthA)) {
System.out.println("两边之和必须大于第三个边");
System.exit(0);
}
double p = (lengthA+lengthB+lengthC)/2;
double b = Math.sqrt(p*(p-lengthA)*(p-lengthB)*(p-lengthC));
super.setArea(b);
}
public void outInfo() {
this.girth();
this.area();
System.out.println("所求三角形周长为："+super.getGirth());
System.out.println("所求三角形面积为："+super.getArea());
}
}
public class ShapeTest {
public static void main (String [] args){
Shape circle = new Circle(3.0);
Shape rectangle = new Rectangle(8.0,7.0);
Shape triangle = new Triangle(3.0,4.0,5.0);
circle.outInfo();
rectangle.outInfo();
triangle.outInfo();
}
}
楼主是不是想利用Java求shape文件中 面的面积，也就是polygon或者multipolygon的面积。实际上就是不规则多边形的面积，如果不用什么函数库（geotools）的话，还是有现成的公式的，非是通过定积分推倒了一个公式而已。\x0d\x0a需要注意的是:\x0d\x0a点要按照逆时针或者顺时针的顺序添加进list\x0d\x0apackage geodemo;\x0d\x0aimport java.awt.Point;\x0d\x0aimport java.util.ArrayList;\x0d\x0aimport java.util.List;\x0d\x0aimport org.opengis.feature.simple.SimpleFeature;\x0d\x0aimport com.vividsolutions.jts.geom.Geometry;\x0d\x0apublic class GetArea{\x0d\x0apublic static void main(String args[]){\x0d\x0aPoint p1 = new Point(1,0);\x0d\x0aPoint p2 = new Point(12,0);\x0d\x0aPoint p3 = new Point(10,10);\x0d\x0aPoint p4 = new Point(0,10);\x0d\x0aPoint p5= new Point(3,3);\x0d\x0aList list = new ArrayList();//泛型\x0d\x0alist.add(p1);\x0d\x0alist.add(p2);\x0d\x0alist.add(p3);\x0d\x0alist.add(p4);\x0d\x0alist.add(p5);\x0d\x0aGetArea t = new GetArea();\x0d\x0adouble area = t.getArea(list);\x0d\x0aSystem.out.println(area);\x0d\x0a}\x0d\x0apublic double getArea(List list)\x0d\x0a{\x0d\x0a//S = 0.5 * ( (x0*y1-x1*y0) + (x1*y2-x2*y1) + ... + (xn*y0-x0*yn) )\x0d\x0adouble area = 0.00;\x0d\x0afor(int i = 0;i
回答于 2022-11-16
Java程序：
public class Main {
public static void main(String[] args) {
Shape s = null;
s = new Circle(3);
System.out.println("圆的面积：" + s.area());
System.out.println("圆的周长：" + s.perimeter());
}
}
/**
* 形状类：抽象类
* @author developer
* @version 2017.05.23
*/
abstract class Shape {
/**
* 计算形状的面积
* @return 形状的面积
*/
abstract double area();
/**
* 计算形状的周长
* @return 形状的周长
*/
abstract double perimeter();
}
/**
* 圆类
* @author developer
* @version 2017.05.23
*/
class Circle extends Shape {
/**
* 半径
*/
protected double radius;
/**
* 构造方法
* @param radius 半径
*/
public Circle(double radius) {
this.radius = radius;
}
@Override
double area() {
return Math.PI * radius * radius;
}
@Override
double perimeter() {
return 2 * Math.PI * radius;
}
}
运行测试：
圆的面积：28.274333882308138
圆的周长：18.84955592153876
Shape.java接口代码
public interface Shape {
public static final double PI = 3.14d;
public double area();
}
Circle.java圆类代码
public class Circle implements Shape {
private double radius;
public Circle(double radius) {
this.radius = radius;
}
@Override
public double area() {
return PI * this.radius * this.radius;
}
public double perimeter() {
return 2 * PI * this.radius;
}
}
Cylinder.java圆柱体类代码
public class Cylinder extends Circle {
private double height;
public Cylinder(double radius, double height) {
super(radius);
this.height = height;
}
public double area() {
return 2 * super.area() + super.perimeter() * this.height;
}
public double volume() {
return super.area() * this.height;
}
}
X5_3_6.java主类代码
public class X5_3_6 {
public static void main(String[] args) {
Circle cir1 = new Circle(5);
System.out.println("圆的面积为：" + cir1.area());
System.out.println("圆的周长为：" + cir1.perimeter());
Cylinder cy1 = new Cylinder(10, 15);
System.out.println("圆柱体的表面积为：" + cy1.area());
System.out.println("圆柱体的体积为：" + cy1.volume());
}
}
上面是我写的代码，下图是执行结果，麻烦看一下，是否可以。
public class Circle implements Shape{
public static void main(String[] args) {
Circle circle = new Circle();
float r = 5; //半径
System.out.println("圆面积：" + circle.getArea(r));
System.out.println("圆周长：" + circle.getCircumference(r));
}
@Override
public float getArea(float a) {
float pi = (float) Math.PI;
return pi * a * a;
}
@Override
public float getCircumference(float a) {
float pi = (float) Math.PI;
return 2 * pi * a;
}
}
public interface Shape {
float getArea(float a);
float getCircumference (float a);
}