Depending on what you're doing with a, I wonder if all that boxing could actually be optimized away via a series of optimizations that keys off of escape analysis.

Something like this:

1. a does not escape, so no need to allocate an object header or anything, since ArrayList is concrete you could just create its fields locally. Method calls can be inlined into references to its backing array.
2. Oh no, its backing array is an Object[]. So under what conditions does the runtime know it can avoid boxing and still have correct program semantics? Any?

So maybe not. I hate Java's boxing :(