Question

3、抽象类练习 图形抽象类，含求周长和面积方法，写一个具体的图形继承该抽象类，如圆

Answer 1

图形抽象类的代码：
abstract class MyShape {
abstract int calGirth(); //求周长
abstract double calSquare(); //求面积
}
三角形类的实现：
public class Triangle extends MyShape{
int borderA, borderB, borderC;

Triangle(int a, int b, int c)
Triangle()

@Override
int calGirth() {
return borderA + borderB + borderC;
}

@Override
double calSquare() {
double p = calGirth() / 2;
return Math.sqrt(p * (p - borderA) * (p - borderB) * (p - borderC));
}

public static void main(String[] args) {
Triangle test = new Triangle(3, 4, 5);
System.out.println("The girth of the triangle is " + test.calGirth());
System.out.println("The square of the triangle is " + test.calSquare());
}
}
实现两个抽象函数，测试结果正确，输出为：
The girth of the triangle is 12
The square of the triangle is 6.0

Answer 2

abstract class graph{
public float getCircum();
public float getArea();
}
class circle extends graph{
private float p=3.14159f;
private float r;
public circle(float r){
this.r=r;
}
public float getCircum(){
return 2*p*r;
}
public float getArea(){
return p*r*r;
}
}