Question

阅读了这个问题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类Animal（超类）和类Dog（子类）如下：

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();
}
}

在实例化类之前，确定需要初始化其直接超类（因此需要执行所有静态变量和块）。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，控制下到静态变量初始化的子类而不是实例成员的初始化呢？

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

这样做的原因是什么，而不是：

superclass -> static members
superclass -> instance members
subclass -> static members
sublcass-> instance members

Answer 1

为什么在初始化超类的静态变量和静态块之后，控制会转到静态变量初始化的子类，而不是完成实例成员的初始化？

因为静态初始化发生一次，所以在创建任何实例之前。

静态对应于类，非静态对应于特定实例。

Answer 2

如果你创造更多狗

是有道理的

superclass (Animal): static variables and static blocks
subclass   (Dog)   : static variables and static blocks

superclass (Animal): instance variables and instance blocks
subclass   (Dog)   : instance variables and instance blocks

superclass (Animal): instance variables and instance blocks
subclass   (Dog)   : instance variables and instance blocks

superclass (Animal): instance variables and instance blocks
subclass   (Dog)   : instance variables and instance blocks

static block instance block java Order

2 个答案: