What is the initialization order of the members after the class is created?

Don't think about inheritance first

package com;

public class DemoOne {
    /**
     * On the initialization order of classes
     */
    //Regardless of inheritance structure
    private static int a;
    private String  str="I'm assigned a value";
    {
        System.out.println("3 Enter code block  str ===="+ str);
        System.out.println("4 Go to normal code block");


    }
    static{
        System.out.println("1 Static code block a==="+a);
        //here a The initial value 0 indicates that the static variable executes before the static code block because of the sequence of the code
        //  Compile and report errors     System.out.println("str ===="+ str);
        System.out.println("2 Enter static code block");


    }
    public DemoOne(){
        System.out.println("5 Enter constructor");
        System.out.println(" Constructor str===="+str);
        System.out.println("a===="+a);

    }

    public static void main(String[] args) {
        new  DemoOne();
    }

}

The output after running the program is:

1 static code block a = 0
2 enter static code block
str = = = in code block 3
4 into normal code block
5 enter the constructor
str = = = I'm assigned a value in the constructor
a====0

To verify that the order of static members is determined by the order of the code, static variables and static block order are adjusted

package com;

public class DemoOne {
    /**
     * On the initialization order of classes
     */
    //Regardless of inheritance structure
    static{
        //  Compile and report errors     System.out.println("str ===="+ str);
        System.out.println("1 Enter the first static code block");
    }
    private static int a;
    static{
        System.out.println("2 Enter the second static block a===="+a);
    }
    private String  str="I'm assigned a value";
    {
        System.out.println("3 Enter code block  str ===="+ str);
        System.out.println("4 Go to normal code block");


    }

    public DemoOne(){
        System.out.println("5 Enter constructor");
        System.out.println(" Constructor str===="+str);
        System.out.println("a===="+a);

    }

    public static void main(String[] args) {
        new  DemoOne();
    }

}

The output result is:

1 enters the first static code block
2 enter the second static block a = ==== 0
3 enter the code block str = = = I have been assigned a value
4 into normal code block
5 enter the constructor
str = = = I'm assigned a value in the constructor
a====0

From the output result, we can see that the static block and the sequence of static variables have changed after adjusting the sequence