11. 创建一个名为“shape”的抽象类，该类内部含有两个抽象方法getGirth(int i)和getArea(int i)，分别用来计算周长和面积；“shape”类派生出子类“triangle”，“triangle”类中按照三角形的周长和面积的计算方式对“shape”类中两个抽象方法进行覆盖，triangle构造方法具有六个参数，分别为三个顶点的横坐标和纵坐标，并在main方法中进行验证。请写出Shape、triangle类的源代码并设置用例计算输出三角形的周长和面积（注：可使用Math类）。用Java

Shape类的源代码如下：

public abstract class Shape {
    public abstract double getGirth(int i);
    public abstract double getArea(int i);
}

Triangle类的源代码如下：

public class Triangle extends Shape {
    private double x1, y1, x2, y2, x3, y3;
    
    public Triangle(double x1, double y1, double x2, double y2, double x3, double y3) {
        this.x1 = x1;
        this.y1 = y1;
        this.x2 = x2;
        this.y2 = y2;
        this.x3 = x3;
        this.y3 = y3;
    }
    
    @Override
    public double getGirth(int i) {
        double ab = Math.sqrt(Math.pow(x1 - x2, 2) + Math.pow(y1 - y2, 2));
        double bc = Math.sqrt(Math.pow(x2 - x3, 2) + Math.pow(y2 - y3, 2));
        double ac = Math.sqrt(Math.pow(x1 - x3, 2) + Math.pow(y1 - y3, 2));
        return ab + bc + ac;
    }
    
    @Override
    public double getArea(int i) {
        double ab = Math.sqrt(Math.pow(x1 - x2, 2) + Math.pow(y1 - y2, 2));
        double bc = Math.sqrt(Math.pow(x2 - x3, 2) + Math.pow(y2 - y3, 2));
        double ac = Math.sqrt(Math.pow(x1 - x3, 2) + Math.pow(y1 - y3, 2));
        double p = (ab + bc + ac) / 2;
        return Math.sqrt(p * (p - ab) * (p - bc) * (p - ac));
    }
}

用例代码如下：

public class Test {
    public static void main(String[] args) {
        Triangle t = new Triangle(0, 0, 3, 0, 0, 4);
        System.out.println("周长：" + t.getGirth(0));
        System.out.println("面积：" + t.getArea(0));
    }
}

运行结果：

周长：12.0
面积：6.0