【发布时间】:2013-03-06 17:46:56
【问题描述】:
已阅读此问题In what order are the different parts of a class initialized when a class is loaded in the JVM? 和相关的 JLS。我想更详细地了解为什么例如具有以下动物类(超类)和狗类(子类):
class Animal
{
static{
System.out.println("This is Animal's static block speaking"):
}
{
System.out.println("This is Animal's instance block speaking");
}
class Dog{
static{
System.out.println("This is Dog's static block speaking");
}
{
System.out.println("This is Dog's instance block speaking");
}
public static void main (String [] args)
{
Dog dog = new Dog();
}
}
好的,在实例化一个类之前,它的直接超类需要被初始化(因此所有的静态变量和块都需要被执行)。 所以基本上问题是:为什么在初始化超类的静态变量和静态块之后,控制权交给子类进行静态变量初始化,而不是完成实例成员的初始化?
控制如下:
superclass (Animal): static variables and static blocks
subclass (Dog): static variables and static blocks
superclass (Animal): instance variables and instance blocks
sublcass (Dog):instance variables and instance blocks
是什么原因导致是这样而不是:
superclass -> static members
superclass -> instance members
subclass -> static members
sublcass-> instance members
【问题讨论】:
-
我正在努力想出一个这甚至很重要的例子(鉴于超类对子类一无所知)。