java - 抽象类: output of this code

Question

目前正在对抽象类和接口(interface)进行实践测试，遇到了这个问题:

  public class Test {
  public static void main(String[] args) {
    new Circle9();
  }
}

public abstract class GeometricObject {
  protected GeometricObject() {
    System.out.print("A");
  }

  protected GeometricObject(String color, boolean filled) {
    System.out.print("B");
  }
}

public class Circle9 extends GeometricObject {
  /** Default constructor */
  public Circle9() {
    this(1.0);
    System.out.print("C");
  }

  /** Construct circle with a specified radius */
  public Circle9(double radius) {
    this(radius, "white", false);
    System.out.print("D");
  }

  /** Construct a circle with specified radius, filled, and color */
  public Circle9(double radius, String color, boolean filled) {
    super(color, filled);
    System.out.print("E");
  }

}

为什么输出是BEDC？我认为 new Circle9() 会首先调用 Circle 9 类的无参数构造函数，打印 A，然后打印其他字母，但我很难理解代码的路径。

Answer 1

跟踪调用堆栈:

• new Circle9() 调用 Circle9()
• Circle9() 调用 this(1.0)
• Circle9(double) 调用 this(radius, "white", false)
• Circle9(double, String, boolean) 调用 super(color,filled)
• GeometricObject(String, boolean) 打印 B
• Circle9(double, String, boolean) 打印 E
• Circle9(double) 打印 D
• Circle9() 打印 C