Java block as a class member

Do you know code block? Of course you know! Block of code defines the scope of variables and puts more statemets together. But what about non-static blocks as a class member? You can put them as other class members such as static blocks, class variables and methods.

E.g. static block is executed after class is loaded. This example is clasic block of code...

{ 
    // block of statements: Fibonacci series
    int s, f1 = 0, f2 = 1;
    while (f1 < 100) {
        System.out.println(f1);
        s = (f1 + f2);
        f1 = f2;
        f2 = s;
    }
}

And now, try to find non-static block inside BlockTest class...

public class BlockTest {

 // field without explicit initialization
 private int id;

 // field with ininitialization
 private String value = "UNDEF";

 static {
     System.out.println("static code: executed onece when the class is loaded\n");
 }

 {
     System.out.println(debug("executed before constructor, but after members initialization"));
 }

 // constructor
 public BlockTest(int id, String value) {
     this.id = id;
     this.value = value;
     System.out.println(this.debug("constructor"));
 }

 String debug(String msg) {
     return String.format("%d - %5s: %s", this.id, this.value, msg);
 }

 // main method
 public static void main(String[] args) {
     new BlockTest(1, "one");
     new BlockTest(2, "two");
     new BlockTest(3, "three");
 }

}