Java程序初始化顺序

import java.util.*;






public class Demo ...{




static ...{




System.out.println("i am static demo.");


}




...{




System.out.println("i am demo.");


}




static void print()...{


System.out.println("can omit instance initialization?");


}




public static void main(String[] args) ...{


new Sub("child");


Demo.print();


}


}






abstract class Base ...{


public String name = " ";


public String sex="base";




public Base(String name) ...{


System.out.println("name:" + this.name);


this.name = name;


System.out.println("invoke base constructor");


System.out.println("name:" + name);


this.setName("parent");


}






...{


System.out.println("invoke base instance block");


System.out.println("this.sex:"+this.sex);


printInfo();


}






static ...{


System.out.println("invoke base static block");


}




// public abstract void setName();




public abstract void printInfo();






public void setName(String name) ...{


this.name = name;


System.out.println("invoke parent setName method");


System.out.println("name:" + name);


}




}






class Sub extends Base ...{


public static int age = 10;


public String sex="sub";




public Sub(String name) ...{


super(name);


System.out.println("invoke sub constructor");


System.out.println("name:" + name);


}






...{


System.out.println("invoke sub instance block");


System.out.println("name:" + name);


}






static ...{


System.out.println("invoke sub static block");


}






public void printInfo() ...{


System.out.println(" ");


System.out.println("invoke sub printInfo");


System.out.println("age:" + age);


System.out.println("name:" + name);


System.out.println(" ");


}






public void setName(String name) ...{


System.out.println("invoke sub setName method");


this.name = name;


System.out.println("name:" + name);


}


}

输出结果；

i am static demo.
invoke base static block
invoke sub static block
invoke base instance block
this.sex:base

invoke sub printInfo
age:10
name:

name:
invoke base constructor
name:child
invoke sub setName method
name:parent
invoke sub instance block
name:parent
invoke sub constructor
name:child
can omit instance initialization?
初始化的实际过程为：

在其它任何事物发生之前，将分配给对象的存储空间初始化成二进制的零。

父类static 块或变量

子类static块或变量

父类的显式初始化

父类构造函数

子类的显式初始化

子类的构造函数

此过程中若有父类构造体中调用方法可被子类重载，则JVM会从最低子类对象处寻找此方法，找到则执行，虽然此时对象还未完全生成（可能会造成潜在的错误）。