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java继承的一个问题

摘要: java继承的一个问题

写一个程序，建一个三角形的类，一个长方形的类，他们都继承多边形类，都要实现接口，包括计算三角形和长方形的周长以及他们的周长差（写函数）

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public class Test {
public static void main(String[] args) {
int a = 0, b = 0, c = 0;
Rectangle r=new Rectangle(a, b);
System.out.println(r.circum());
Triangle t=new Triangle(a, b, c);
System.out.println(t.circum());
System.out.println(r.circum()-t.circum());
}
}
interface Polygon {
public double circum();
}
class Rectangle implements Polygon {
private double x, y;
Rectangle(double x, double y) {
this.x = x;
this.y = y;
}
public double circum() {
return 2 * (x + y);
}
}
class Triangle implements Polygon {
private double x, y, z;
Triangle(double x, double y, double z) {
this.x = x;
this.y = y;
this.z = z;
}
public double circum() {
return x + y + z;
}
}

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========Interface=========
package alex.interfaces;

public interface polygon {
/**
* 计算多边形周长
* @return
*/
public double calculateGirth();

}
================Class===============
package alex.graphic;

import alex.interfaces.polygon;

public abstract class abstractPolygon implements polygon {

public abstract double calculateGirth();

/**
* 计算两个多边形的周长差
* @param obj
* @return
*/
public abstract double calculateGirthDiffrence(abstractPolygon obj);

}




package alex.graphic;

public class Rectangle extends abstractPolygon {

private double width,height;

public Rectangle(){
this.width = 0;
this.height = 0;
}

public Rectangle(double w, double h){
this.width = w;
this.height = h;
}

public double calculateGirth() {
return (this.width + this.height)*2;
}

public double calculateGirthDiffrence(abstractPolygon obj) {
return this.calculateGirth() - obj.calculateGirth();
}

}







package alex.graphic;

public class Triangle extends abstractPolygon {

private double x1,x2,x3;

public Triangle(){
this.x1 = 0;
this.x2 = 0;
this.x3 = 0;
}

public Triangle(double line1, double line2, double line3){
this.x1 = line1;
this.x2 = line2;
this.x3 = line3;
}

public double calculateGirth() {
return x1+x2+x3;
}

public double calculateGirthDiffrence(abstractPolygon obj) {
return this.calculateGirth() - obj.calculateGirth();
}

}





package alex.graphic;

public class test {
public static void main(String[] args){
Rectangle r = new Rectangle(20,10);
Triangle t = new Triangle(3,4,5);
System.out.println("矩形周长＝"+r.calculateGirth());
System.out.println("三角形周长＝"+t.calculateGirth());
System.out.println("矩形－三角形周长差＝"+r.calculateGirthDiffrence(t));
}
}

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