In Java and Android, the order in which blocks of code, static code blocks are executed

In Java and Android, what is the difference between the execution order of blocks of code and static code blocks?

Java

Let's start with a simple example.

Main.java:

publicclass Main {    staticint1;    static {        System.out.println(a);    }    static {        2;    }    publicstaticvoidmain(String[] args) {        System.out.println("Hello World!");        System.out.println(a);    }}

Output to

1
Hello world!
2

After attempting to exchange static variable declarations and static code blocks, compile an error "illegal forward reference".
Interactive two code block position after output

2
Hello world!
2

Visible static decorated, from top to bottom, executed sequentially. Static variables and code blocks take precedence

Let's do a more complicated experiment.

 Public  class Main {    Static intA =1;Static{System.out.println (a); }Static{a =2; } Public Static void Main(string[] args) {System.out.println ("Hello world!");        Yo.test (); Yo yooo =NewYo ();    Yooo.test (); }} Public  class Yo {    StaticString name ="Mark";Static{System.out.println (name); } Public Yo() {Super(); System.out.println ("Constructor"); }Static  Public void Test() {System.out.println ("Hello"+ name); }}

Output

1
Hello world!
Mark
Hello Mark
Constructor
Hello Mark

Yo's execution conforms to the above conclusion, the static code block is executed, and after you construct the Yo instance, no static code blocks are executed repeatedly.

Android

 Public  class testapplication extends baseapplication {    Static{LOG.D ("Test","Application 1123"); }Static intA =1;Static{LOG.D ("Test","Application"+ a);    Homeactivity.test (); }Static{a =2; }@Override    protected void Attachbasecontext(Context Base) {LOG.D ("Test","Application Hello"+ a); }} Public  class splashactivity extends baseactivity {    Static{LOG.D ("Test","splashactivity Static code block"); }Static intA =1;Static{LOG.D ("Test","Splashactivity"+ a); }Static{a =2; }@Override    protected void onCreate(Bundle savedinstancestate) {LOG.D ("Test","Splashactivity onCreate"+ a);//Omit, will go to start homeactivity}} Public  class homeactivity extends baseactivity {     Public Static FinalString TAG ="Homeactivity";Static{LOG.D ("Test","Homeactivity 1123"); } Public Static void Test() {LOG.D ("Test","Homeactivity"); }}

The output result is

D/test:application 1123
D/test:application 1
D/test:homeactivity 1123
D/test:homeactivity
D/test:application Hello 2
D/test:splashactivity Static code block
D/test:splashactivity 1
D/test:splashactivity OnCreate 2

There's no difference between Java and the results.

The same is done first by static, static initialization of other classes outside the entrance, when the class is loaded by the JVM (from the result, it is loaded when the class is used).

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In Java and Android, the order in which blocks of code, static code blocks are executed