Static code block, code block, constructor execution order

The first is the parent class

public class Father {
 String name;
 int age;

    public Father(String name, int age) {
        this.name = name;
        this.age = age;
        System.out.println(" The parent class has a parametric constructor ");
    }
    public Father(){
        System.out.println(" Parent class parameterless constructor ");
    }

    static {
     System.out.println(" Parent static code block ");
 }

    {
        System.out.println(" The parent class constructs the code block ");
    }
    public  void test1(){
        {
            System.out.println(" Parent normal code block ");
        }
    }
}

Subclass

public class Son extends Father {
    public Son(String name, int age) {

        super(name, age);
        System.out.println(" Subclass parameterized constructor ");
    }

    public Son() {
        System.out.println(" Subclass parameterless constructors ");
    }
   static  {
        System.out.println(" Subclass static code block ");
    }
    {
        System.out.println(" Subclass construct code block ");
    }
    public void test2(){
        {
            System.out.println(" Subclass common code block ");
        }
    }
}

Test class

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

Take a look at the results of the run

  We can see the execution sequence of the parent class static code block

Parent static code block
Subclass static code block
The parent class constructs the code block
Parent class parameterless constructor
Subclass construct code block
Subclass parameterless constructors

We can see that a total of 6 results , So why do we just create an initialization Son, This will happen ？

First ： We create a Son object , Called Son The parameterless constructor of , And ours Son The parameterless constructor will automatically call the parameterless constructor of the parent class .

amount to

  Add ： Even when we create a class , No write constructor ,java We will also add a parameterless constructor by default , If you don't write any constructors .

summary ：

Parent static code block （ Static variables > A static block ） > Static code block of subclass > The parent class constructs the code block 、 Construction method > Construction code block of subclass 、 Construction method