A reply to another question made me remember a project from some years ago when it turned out that Java was not the right tool to use.

I typically only learn a new language when I have a problem that it solves better than the ones I already know. [...]

Then I write whatever program I wanted to learn that language for in the first place. [...] By the time I've gotten my target program written, I've usually got a decent handle on the language, not to mention any other features it has, and I've got other ideas to use it for.

I did just that back then with Java, because the client thought it to be the right language to use (platform independent) and initial evaluation confirmed that.

However, much later in the project there were some issue (can't really remember all the details by now). So, the project that started as a nice learning experience turned into a nightmare toward the end.

I was at the brink of switching over to my trusted C++ and doing a complete rewrite. The client was not so much of a problem to convince back then, but my supervisor was strongly opposed because of all the work that already went into the Java version. In hindsight, he was right and the project was complete more or less with the intended features kind of working, but it was the project that I am least proud of by now.

Long story short: what do you think, when is it too much and the switch to another technology is worthwhile? I personally would estimate the point of no return to be around 50% of the planned effort, but really want to know, if anyone has real experience with such a switch.

And to answer the inevitable question: I do not really care, if the technology switched to is proven or another new thing. The latter would basically need more initial scrutiny based on the past experiences in the problematic project.