android覆蓋子類中的函數

-2

我做了一個類，然後從它的兩個子類。圖超類有一個名爲are（）的方法。這是全班同學。android覆蓋子類中的函數

public class Figure 
{ 
    public double a, b; 
    public Figure(double a,double b) { 
    this.a = a; 
    this.b = b; 
    } 

    public double are() { 
    return 0; 
    } 
} 

public class Rectangle extends Figure 
{ 
    Rectangle(double a, double b) { 
    super(a,b); 
    } 

    double area(){ 
    return this.a*this.b; 
    } 
} 

class Triangle extends Figure 
{ 
    Triangle(double a, double b) { 
    super(a,b); 
    } 
    // override area for right triangle 
    double area() { 
    return a * b/2; 
    } 
}

易打印outpute我做

public void toastM(String str) { 
    Toast.makeText(getApplicationContext(), str, Toast.LENGTH_SHORT).show(); 
}

現在我用這個代碼

Figure f = new Figure(10, 10); 
Rectangle r = new Rectangle(9, 5); 
Triangle t = new Triangle(10, 8); 

Figure figref; 
figref = r; 
toastM("are..... " + figref.are()); 
figref = t; 
toastM("are..... " + figref.are()); 
figref = f; 
toastM("are..... " + figref.are());

預期值45 40 0 但前來0 0 0

來源

2017-07-27 Masoud Masoud

父類的方法名應該與子類中的overriden相同。看[this]（https://www.javatpoint.com/method-overriding-in-java）。如果沒有正確學習概念，不要發佈問題。 –