Tag Archives: HPROF

Hiccups with Java double brace initialization of anonymous object

Double brace initialization is often used technique to overcome Java limitations on working with anonymous objects. In my case I used HashMap to pass tracking event parameters to Flurry Analytics class. The code is like this :

final HashMap<String, String> eventParms = new HashMap<String, String>() {{
    put("fileSize", Long.toString(new File(item.path).length()));
    put("mimeType", mimeType);
}};
FlurryAgent.logEvent(event , eventParms);

Looks pretty nice, and avoids creating local variable and then putting parameter pairs into it. However I started seeing OutOfMemoryExceptions in my Android application. I took HPROF memory dump, and pretty quickly realized that the problem was with anonymous classes they somehow were of a huge size. I googled around and found this article : http://vanillajava.blogspot.ru/2011/06/java-secret-double-brace-initialization.html, and it became obvious that it was exactly my problem: Anonymous object retained reference to outer class, which in my case had members of a big size – Bitmaps etc. So while Flurry events were kept int the queue those huge bitmaps ere also occupying heap memory.

Additional note on HPROF: In order to use standard Memory Analyzer tool you need to convert HPROF heap dump from Android format to regular Java format. Use android_sdk/tools/hprof-conv.