Java Question

The project that I am currently working on has an interesting issue.  We just started using a tool called YourKit Java Profiler, and it shows that we have 26 MB of duplicate copies of the empty string "".  My first reaction was shock: I thought all compilers were smart enough to recognize that immutable strings (such as string constants) that are identical should reference a single version of that string.  But if YourKit Java Profiler is to be believed, that is NOT happening.  I asked the question here, and the answers that I received indicated that Java does create only a single version of a string constant -- but that the problem might be:

String str = i + ""

which is a very common Java construct for converting an integer to a string, is turning into something like:

String str = new StringBuilder("").append(i).toString();  

The implication is that the new StringBuilder("") is producing a distinct object each time, because that is a mutable string.  The solution is to use the somewhat less easy 

String.valueOf(i)

to produce the string version of i instead.  Does this seem like a plausible explanation of how we end up with 26 MB of "" copies?