定义了一个抽象类A，里面有抽象函数
定义一个类B继承抽象类A，重写抽象函数
在test类里面如何对B实例化，实现B的函数。
我用new会一直报错，看其他贴都是这样写
```java
import java.util.Scanner;
abstract class PlaneGraphic {
public abstract void triangleS();
public abstract void triangleC();
}
abstract class Triangle extends PlaneGraphic {
double a;
double b;
double c;
public Triangle(double a, double b, double c){
this.a = a;
this.b = b;
this.c = c;
}
public void triangleC(){
double p = a + b + c;
System.out.println("三角形周长为:" + p);
}
public void triangleS(){
double p = (a + b + c) / 2;
double s = Math.sqrt(p * (p - a) * (p - b) * (p - c));
System.out.println("三角形的面积为:" + s);
}
}
public class Test
{
public static void main(String[] args)
{
Scanner input = new Scanner(System.in);
double a, b, c;
System.out.println("输入三角形的三边长度");
a = input.nextDouble();
b = input.nextDouble();
c = input.nextDouble();
PlaneGraphic tri = new Triangle(a, b, c);
tri.triangleC();
tri.triangleS();
}
}
报错内容
