Double Brace Initialization

http://www.c2.com/cgi/wiki?DoubleBraceInitialization



To pass a set to a method:

 Set<String> validCodes = new HashSet<String>();
 validCodes.add("XZ13s");
 validCodes.add("AB21/X");
 validCodes.add("YYLEX");
 validCodes.add("AR2D");
 removeProductsWithCodeIn(validCodes);

Or to initialize a set of constants:

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

But... you can create and initialize a new collection as an expression by using the "double-brace" syntax: E.g.

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

Or:

 removeProductsWithCodeIn(new HashSet<String>() {{
 add("XZ13s");
 add("AB21/X");
 add("YYLEX");
 add("AR5E");
 }});