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-rw-r--r--java.html.markdown27
1 files changed, 27 insertions, 0 deletions
diff --git a/java.html.markdown b/java.html.markdown
index e4234a39..478ec683 100644
--- a/java.html.markdown
+++ b/java.html.markdown
@@ -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, by 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