理解javap输出

Question

我有一个非常简单的类:

package MyDev;
public class Point3D  {
   public Point3D(){x = 0; y = 0;z = 0;}
   public float x, y, z;
   public Point3D( float X, float Y, float Z ) 
   {
      x = X;  y = Y;  z = Z;
   }
}

当我在这个类上运行javap -c时，我得到的是:

C:ProjectsDevelopmentMyJavabinMyDev>"C:Program Files (x86)Javajdk1.7.0_55binjavap" -c Point3D.class
Compiled from "Point3D.java"
public class MyDev.Point3D {
  public float x;
  public float y;
  public float z;
  public MyDev.Point3D();
    Code:
       0: aload_0
       1: invokespecial #12                 // Method java/lang/Object."<init>":()V
       4: aload_0
       5: fconst_0
       6: putfield      #14                 // Field x:F
       9: aload_0
      10: fconst_0
      11: putfield      #16                 // Field y:F
      14: aload_0
      15: fconst_0
      16: putfield      #18                 // Field z:F
      19: return
  public MyDev.Point3D(float, float, float);
    Code:
       0: aload_0
       1: invokespecial #12                 // Method java/lang/Object."<init>":()V
       4: aload_0
       5: fload_1
       6: putfield      #14                 // Field x:F
       9: aload_0
      10: fload_2
      11: putfield      #16                 // Field y:F
      14: aload_0
      15: fload_3
      16: putfield      #18                 // Field z:F
      19: return
}

为什么?为什么第二个构造函数也有签名()V，而不是(FFF)V ?我怎么也搞不懂!

Answer 1

这是对Object的构造函数的调用。对父类构造函数的调用总是构造函数中发生的第一件事。