如何从重写的子类方法调用父类的继承方法?[副本]

形状 有toString()方法的。我还有一节课 圆圈 圆圈 形状的 toString()方法 里面 这个 toString()方法。以下是我目前所做的。我想在 圆圈

形状类别:

class shape{
String color;
boolean filled;
shape()
{
    color = "green";
    filled = true;
}
shape(String color, boolean fill)
{
    this.color = color;
    this.filled = fill;
}
public String toString()
{
    String str = "A Shape with color = " + color + " and filled = " + filled + " .";
    return str;
}
}

圆圈类:

class circle extends shape
{
double radius;
circle()
{
    this.radius = 1.0;
}
public String toString()
{
    String str = "A circle with radius " + radius + " and which is a subclass of " + toString();
    return str;
}

请帮忙!