class pramid extends rectangle对吗？？
应该是class pramid extends triangle 吧。。。

是我不用心，因为没想到自己会犯这种1+1的问题，见笑

class triangle {
    double a;
    double b;
    double c;

    public triangle(double a, double b, double c) {
        if ((a + b > c) && (a + c > b) && (b + c > a) && (a - c < b)
                && (a - b < c) && (b - c < a)) {

            this.a = a;
            this.b = b;
            this.c = c;
        } else {
            System.out.println("输入边长有错");
        }

    }

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

    public double GetArea() {
        double p;
        p = (a + b + c) / 2.0;
        return (Math.sqrt(p * (p - a) * (p - b) * (p - c)));
    }


class Tprism extends triangle {
    double height;

    public Tprism(double a, double b, double c, double height) {
        super(a, b, c);

        if ((a + b > c) && (a + c > b) && (b + c > a) && (a - c < b)
                && (a - b < c) && (b - c < a)) {

            this.a = a;
            this.b = b;
            this.c = c;
            this.height = height;
        } else {
            System.out.println("输入边长有错");
        }

    }
}
    public static void main(String[] args) {

        triangle r = new triangle(3.0, 4.0, 5.0);
        triangle.Tprism c=r.new Tprism(3.0,4.0,5.0,6.0);
        System.out.println("三角形的周长" + r.GetCircle());
        System.out.println("三角形的面积" + r.GetArea());
        System.out.println("三棱柱的底面积" + c.GetCircle());
        System.out.println("三棱柱的底周长" + c.GetArea());
        System.out.println("三棱柱的体积" + c.GetArea() * c.height);
    }
}
第一道题的代码可以用内部类调用完成