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 VALID_CODES = new HashSet() {{
    add("XZ13s");
    add("AB21/X");
    add("YYLEX");
    add("AR2D");
}};