Your tutor misdiagnosed the issue. These allocations in a tight loop would have used bump allocation on Java 6 in 2010, and the young generation would have used a copy collector, which would have freed those objects more cheaply than any unspecialized malloc/free. It would have beaten the pants off of PHP's reference counting GC.
I remember now what the problem was. I was instantiating a new ArrayList in a loop. The solution to the performance issue was to use a Vector instead. I was used to just writing PHP arrays when I wanted a list of something, and since they’re dynamically sized I thought the analogue in Java was ArrayList, which is also dynamically sized. But somehow that was extremely unperformant in Java.
