What kind of runtime optimizations are lost if we use reflection

Question

In this discussion about the performance overhead of using reflection, it is stated:

Use of reflection can cause some runtime optimizations to be lost. For example, the following code is highly likely be optimized by a Java virtual machine:

int x = 1;
x = 2;
x = 3;

Equivalent code using Field.set*() may not.

Without reflection, what kind of runtime optimizations would be done by JVM?

Answer 1

In this case the code can be discarded as it doesn't appear to do anything.

If you used reflection I suspect it would still do something although you can't access a local variable using reflection.