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我有一个扩展到两个子类（CircleFromSimpleGeometricObject和RectangleFromSimpleGeometricObject）的超类（SimpleGeometricObject），以及一个调用CircleFromSimpleGeometricObject和RectangleFromSimpleGeometricObject的类，名为TestCircleRectangle。继调试，为子类CircleFromSumpleGeometricObject， 这行代码：Java超类继承
public CircleFromSimpleGeometricObject(double radius){
this.radius = radius;
}
莫名其妙地调用超SimpleGeometricObject：
/** Construct a default geometric object */
public SimpleGeometricObject() {
dateCreated = new java.util.Date();
}
我有点困惑如何发生以及为什么有人可以帮助我理解为什么发生这种情况以下是所有课程的代码。
public class SimpleGeometricObject {
private String color = "white";
private boolean filled;
private java.util.Date dateCreated;
/** Construct a default geometric object */
public SimpleGeometricObject() {
dateCreated = new java.util.Date();
}
/** Construct a geometric object with the specified color
* and filled value */
public SimpleGeometricObject(String color, boolean filled) {
dateCreated = new java.util.Date();
this.color = color;
this.filled = filled;
}
/** Return color */
public String getColor() {
return color;
}
/** Set a new color */
public void setColor(String color) {
this.color = color;
}
/** Return filled. Since filled is boolean,
its get method is named isFilled */
public boolean isFilled() {
return filled;
}
/** Set a new filled */
public void setFilled(boolean filled) {
this.filled = filled;
}
/** Get dateCreated */
public java.util.Date getDateCreated() {
return dateCreated;
}
/** Return a string representation of this object */
public String toString() {
return "created on " + dateCreated + "\ncolor: " + color +
" and filled: " + filled;
}
}
public class CircleFromSimpleGeometricObject
extends SimpleGeometricObject {
private double radius;
public CircleFromSimpleGeometricObject() {
}
public CircleFromSimpleGeometricObject(double radius){
this.radius = radius;
}
public CircleFromSimpleGeometricObject(double radius,
String color, boolean filled) {
this.radius = radius;
setColor(color);
setFilled(filled);
}
/** Return radius */
public double getRadius() {
return radius;
}
/** Set a new radius */
public void setRadius(double radius) {
this.radius = radius;
}
/** Return area */
public double getArea() {
return radius * radius * Math.PI;
}
/** Return diameter */
public double getDiameter() {
return 2 * radius;
}
/** Return perimeter */
public double getPerimeter() {
return 2 * radius * Math.PI;
}
/** Print the circle info */
public void printCircle() {
System.out.println("The circle is created " + getDateCreated() +
" and the radius is " + radius);
}
}
public class RectangleFromSimpleGeometricObject
extends SimpleGeometricObject {
private double width;
private double height;
public RectangleFromSimpleGeometricObject() {
}
public RectangleFromSimpleGeometricObject(
double width, double height) {
this.width = width;
this.height = height;
}
public RectangleFromSimpleGeometricObject(
double width, double height, String color, boolean filled) {
this.width = width;
this.height = height;
setColor(color);
setFilled(filled);
}
/** Return width */
public double getWidth() {
return width;
}
/** Set a new width */
public void setWidth(double width) {
this.width = width;
}
/** Return height */
public double getHeight() {
return height;
}
/** Set a new height */
public void setHeight(double height) {
this.height = height;
}
/** Return area */
public double getArea() {
return width * height;
}
/** Return perimeter */
public double getPerimeter() {
return 2 * (width * height);
}
}
public class TestCircleRectangle {
public static void main(String[] args) {
CircleFromSimpleGeometricObject circle =
new CircleFromSimpleGeometricObject(1);
System.out.println("A circle " + circle.toString());
System.out.println("The color is " + circle.getColor());
System.out.println("The radius is " + circle.getRadius());
System.out.println("The area is " + circle.getArea());
System.out.println("The diamter is " + circle.getDiameter());
RectangleFromSimpleGeometricObject rectangle =
new RectangleFromSimpleGeometricObject(2, 4);
System.out.println("\nA rectangle " + rectangle.toString());
System.out.println("The area is " + rectangle.getArea());
System.out.println("The perimeter is " +
rectangle.getPerimeter());
}
}
我将简化那些名字;好名字很重要。我不明白为什么Circle，Rectangle和AbstractShape不足够。 – duffymo
默认情况下，子类调用超类构造函数。你可以通过调用super –