Unusual “static” method declaration

Question

public class Card {

    public enum Rank { DEUCE, THREE, FOUR, FIVE, SIX,
        SEVEN, EIGHT, NINE, TEN, JACK, QUEEN, KING, ACE }

    public enum Suit { CLUBS, D         


        

Answer 1

As Grzegorz correctly points out, it's a static initializer block.

Here is another resource explaining the difference between class initialization and instantiation, as well as the order in which class variables and static initializer blocks are called.

A related concept is that of instance initializer blocks, which can be used together with anonymous classes for the handy double-brace initialization idiom:

private static final Set<String> VALID_CODES = new HashSet<String>() {{
    add("XZ13s");
    add("AB21/X");
    add("YYLEX");
    add("AR2D");
}};

Answer 2

This is not a method, but a static Initializer block of a class. You can read more about it in the Java Language Specification.

The code within is executed once after loading the class.

Answer 3

It is also good to know initialization order, as I remember first in this order comes static variables, than static block. Also important point is time when this static block executes - at the first mention of corresponding class, not at the class instance creation.