指出如下Java代码的错误并解释原因,如何修改。 public abstract class Shap { public abstract double getArea(); } public class Square extends Shap{ private double height=0;// 正方形边长 public Square(double height) { super(); this.height = height; } public double getArea(){ return height*height; } } public class Triangle extends Shap{ private double height;// 高 private double weight;// 低 public double getArea() { // TODO Auto-generated method stub return (height *weight)/2; } public Triangle(double height, double weight) { super(); this.height = height; this.weight = weight; } } public class Test_Exam4_xuanze { public static void main(String[] args) { Shap square = new Square(4); Shap triangle = new Triangle(20, 40); System.out.println(square.getArea()); System.out.println(triangle.getArea()); Triangle triangle2 =(Triangle) square; triangle2.getArea(); } }