Java中类的继承

// 1 添加一个类表示三角形
package my;

public class Triangle
{
    public double a ;
    public double b ;
    public double c ;
    
    public Triangle()
    {        
    }
    public Triangle (double a, double b , double c )
    {
        this.a = a;
        this.b = b;
        this.c = c;
    }
    
    // 求面积
    public double area()
    {
        double p = (a+b+c)/2;
        double result = Math.sqrt( p * (p-a) * (p-b) * (p-c));
        return result;
    }
}

// 2 添加一个类表示直角三角形，重写area()方法
package my;

public class RightTriangle extends Triangle
{
    @Override
    public double area()
    {
        return a * b / 2;
    }
    
}

// 3 调用
package my;

public class HelloWorld
{
    public static void main(String[] args)
    {
        RightTriangle t = new RightTriangle();
        t.a = 3;
        t.b = 4;
        t.c = 5;
        double area = t.area();
        System.out.println("面积为 ： " + area);
    }
}