Added description for Double Brace Initialization

This commit is contained in:
Per Lilja 2015-10-05 20:29:05 +02:00
parent d1a822f96c
commit 8b45642640

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@ -325,6 +325,33 @@ public class LearnJava {
// toString returns this Object's string representation.
System.out.println("trek info: " + trek.toString());
// Double Brace Initialization
// The Java Language has no syntax for how to create static Collections
// in an easy way. Usually you end up in the following way:
private static final Set<String> COUNTRIES = new HashSet<String>();
static {
validCodes.add("DENMARK");
validCodes.add("SWEDEN");
validCodes.add("FINLAND");
}
// But there's a nifty way to achive the same thing in an
// easier way, buy using something that is called Double Brace
// Initialization.
private static final Set<String> COUNTRIES = HashSet<String>() {{
add("DENMARK");
add("SWEDEN");
add("FINLAND");
}}
// The first brace is creating an new AnonymousInnerClass and the
// second one declares and instance initializer block. This block
// is called with the anonymous inner class is created.
// This does not only work for Collections, it works for all
// non-final classes.
} // End main method
} // End LearnJava class