David M. Lloyd has another piece on modern reflection, this time on VarHandle - and as usual, it's highly informative. It replaces a lot of Unsafe usage, and demonstrates quite a bit of atomic access fundamentals as well, and it opens up offheap access, too.
MethodHandle has been in the JDK since Java 7, and most Java developers have a vague sense that it exists somewhere near invokedynamic and lambda internals. David Lloyd's ongoing series covers the mechanics thoroughly. What it doesn't cover is when you'd actually reach for it - and why.