Static Initializers : static « Modifiers « SCJP

1. SCJP
2. Modifiers
3. static

public class MainClass {
   static double d = 1.23;

 static {
   System.out.println("Static code: d=" + d++);
 }

  public static void main(String args[]) {
   System.out.println("main: d = " + d++);
  }
}

Static code: d=1.23
main: d = 2.23




Static initializers are used to perform processing when a class is first loaded. 
static initializers are executed only once. 
Static initializers are identified by the static keyword followed by code surrounded in curly brackets.


class MainClass{
 static String s = "This code is executed second.";
 String t  = "This code is executed last.";

 static {  // Static initializer
  display("This code is executed first.");
 }
 public static void main(String[] args) {
  display(s);
  MainClass app = new MainClass();
  app.display(app.t);
 }
 static void display(String s) {
  System.out.println(s);
 }
}


This code is executed first.
This code is executed second.
This code is executed last.