Underscores in literals are not supported at this language level

问题

I got this error when creating a final double using underscores to make the double more readable. It was declared in a run() method.

public void run() {        
    final double nanoSeconds = 1_000_000_000.0 / 60.0;    
}

I'm using IntelliJ IDEA 12.

回答1:

In IntelliJ IDEA you have to change Project language level in project settings to 7.0 level:

回答2:

Yes..you need to change the default language level settings if you are using and IDE. For IntelliJ users it is under File --> Project Structure --> Projects.

回答3:

I found with my project that had modules, I had to do this in the modules settings as well.

来源：https://stackoverflow.com/questions/16986346/underscores-in-literals-are-not-supported-at-this-language-level