Because Double Brace Initialization (DBI) creates an anonymous class with a reference to the instance of the owning object, its use can lead to memory leaks if the anonymous inner class is returned and held by other objects. Even when there’s no leak, DBI is so obscure that it’s bound to confuse most maintainers.
For collections, use Arrays.asList
instead, or explicitly add each item directly to the collection.
Map source = new HashMap(){{ // Noncompliant put("firstName", "John"); put("lastName", "Smith"); }};
Map source = new HashMap(); // ... source.put("firstName", "John"); source.put("lastName", "Smith"); // ...