I even did that to myself. I thought about a great product. I was convinced, so I wanted to build it (it would also fulfill my need). Of course then I did research if it already exists. It did. I didn't want it.
I don't want paid compiler too. Native compiler for Java for Android exists (APK precompiler) and it's great.
It's possible to make good java compiler into native code and then sell it to a big corp, but I'm not a big corp, so it's good idea, but I'm not a target audience for it.
I wasn't angry with him, or even annoyed. I simply learned long ago that people who don't have skin in the game rarely give good game advice. People pitch me all the time what programs I should write.
I've written many products over the years, some were successes, others were failures. A common thread has emerged: all the failures were pitched by others. All the successes were ones I wrote to please myself, and everyone told me I was a unique snowflake and nobody else would want it and I would fail.
A: What the world really needs is a native Java compiler. That would be really great! You should write one.
W: I wrote one for Symantec. You can buy it today.
A: I don't want it.