Note that by using a technique known as escape analysis, a virtual machine like the JVM can detect that the lifetime of an object is such that it doesn't leave

Note that by using a technique known as escape analysis, a virtual machine like the JVM can detect that the lifetime of an object is such that it doesn't leave the context of a particular method and then stack-allocate the object implicitly. That may seem like a limited optimization, but when you combine it with method inlining it gets a lot more useful. I believe the optimization is turned off by default in the Sun/Oracle JVM but can be enabled via the -XX:+DoEscapeAnalysis option. For programs that allocate large numbers of short-lived objects, it can make a significant performance difference.